No seriously, I have no freaking idea how to write it so that the words appear to flow naturally.
I mean, this is the best I could come up with as a first page draft. And quite frankly, it is utter shit.

January 8th 2013
10:44AM
Experiment Scene

Synopsis: Vinyl confronts a now ponified Octavia, (Much to her shock and horror) completely loyal to Celestia and the Pony causes of cleansing the Earth of dark impurities. Inner beliefs clash inside Vinyl as she struggles to make it through this inner and outer turmoil. She might have to deal with being interrogated, witnessing the final moments of Octavia's humanity slip away as she is converted, possibly even raped by some sadistic guardpony. Only a false shadow of an exterior of Octavia's former personality will remain, being completely loyal to the regime. Either that, her food is spiked, and when they realized what happened, its too late, for Octavia starts to change right in front of Vinyl's eyes, losing her memories the further the transformation progresses, suppressed if you will. That, and a growing loyalty to Celestia. Octavia could only sob as her very being is corrupted and turned into something she wasn't, while Vinyl can only watch in horror.

“Ugh... I am starting to feel dizzy Vinyl. I-I can't... Ugh...” Octavia slumped off the chair.

“Tavi!” Vinyl yelled in alarm, quickly rushing to the cellist side.

“Augh- it hurts Vinyl. M-my chest-, it feels like its on fire.”

SCRAP FOR LATER USE

“Something in the food... Octavia got that cake unsigned, that would mean...” She paused as she began to fully realize the ramifications of what was happening. “-then that would mean...”

“V-Viynl, I can't breathe.”

Vinyl' turned her head back on her girlfriend, only for her thoughts to come to a screeching halt as her gaze slowly started to settle back on Octavia, becoming paler the further her gaze went. Grey fur had already sprouted up all over her body. But what happened in the next few moments would come to haunt Vinyl for the rest of her life.

Without warning, Octavia began to convulse, before screams of pain seared itself into eardrums. Before the DJ could even blink, one of Octavia's hands had already been reduced to a shriveled hoof, Octavia could only whimper in pain as her bones cracked and shifted, slowly forming to suit that of an equine body.

“No...” Vinyl's gut lurched as she saw a cutie mark flash right into existence,

“N

Any ideas on what to do so I can improve?

Since I am a transformation enthusiast myself. I'll try my best to help you and give you the kind of advice that you want on transformation sequences. My first suggestion is that you should take a look at the beginning of my chapters in my story, each chapter starts out with a transformation of a woman becoming their pony counterpart. I have Twilight's transformation in the first chapter and in the second chapter Lyra and Bonbon's transformation, with Lyra witnessing Bonbon's change first before hers. Taking a look at how others write transformation sequences in their stories might help you come up with an idea of how to write your own transformation sequences.

Well just to make sure you don't run into transformations that are fetishized, I suggest you turn your mature content off, or is it on-I don't know, whatever you do to make that doesn't allow you to see adult or mature fics. The difference between a normal transformation sequence and a fetishized transformation is that the fetishized ones include details that non pornagraphic people really don't need to know or care, especially if target audience are not the fetishists. The fetishized ones involve: The changing of genitals, transformation during sex and/or rape, and transformation that for some reason makes the victim mastrubate during the change. I think that's enough for the Too Much Information on the subject of fetishized transformation and what you should avoid writing if you don't want the transformation sequence to become one of those. That was just a warning to the kind of transformation sequences you might run into if you can see mature and adult rated stuff. However that will probably only work for certain sites that you are a part of rather than the internet in general. Also, that warning is for everyone else reading the thread as well.

Anyway, back on topic, the next thing I would suggest about writing transformation sequence is asking what the ponies look like if they're still like their cartoony selves but somewhat realistic like Smash Bros. Sonic and Lucario or having some sort of strange Robert Rabbit Effect then I can probably help you out on this when I get to the tips of making transformation from human into ponies. Bascially I'm asking you what do the ponies look like in your story is that describing what the characters look like is vital (well at least to me it is) before and after the transformation. Are the ponies big enough to reach your chest or are they small like a dog? Can you see their hooves like how some artists draw them or are they like their cannoical versions in that you can't really unlesss they're unshorned like Big Mac's? Figuring what they look like will help you plan out the transformation sequence and how each part of the change will affect the character.

Next suggestion is how does the transformation affect the character, is the transformation painful, strange (the character feels tingly), or weird (one second the character's hand is normal, the next time they look at it, they see a hoof instead)? Since the transformation is painful, you should note on how much it hurts Octavia to turn into a pony, but you need to find a balance to describe the pain as her body changes. Also you need to decide whether the pain ends halfway through the change or as the transformation ends. How the transformation affects the character leads to my next suggesion...

Consider how fast you want the transformation to go: if you want it to be fast then there's no need to get into that much detail in the changes of Octavia. If you want it to be slow then you have all the time to describe in explicit detail (not that kind of explicit detail) how each part of body changes into that of a pony, not to mention you'll also have time to write about the characterization of Vinyl and Octavia's friendship. Basically have them talk to each other about the good times they have before it becomes "perverted by the pony brainwashing," kind of like how I did with Rarity talking to the scientist who changes her in to her pony form. If you want it to go smoothly or normal pace, I suggest you should try to have at least two sentences describing the change... I think that's all I have at this moment.

Now here are some tips about writing about a person turning into a pony:
The Head: A pony's head, typically a mare, always appear to be circular shape from a humans and the only exception from that rule is if they have a unique design like Fleur or Cadence. Try to write about how a person's head becomes rounder as they turn into a pony. The same goes for a guy becoming a male but more oval shape. However guy's have more of a muzzle than a girl.
Ears: For beginners why don't say there's a pulling sensation in their ears or their ears are pulled to the top corners of their heads
Eyes: It has always been my personal belief that a pony's eyes are always bigger than a human's even if they go up to a human's knees they are still bigger than a human. So at least try to describe how they get big when a person's head turn into a pony.
Forehooves: There are many different styles of how a hand becomes a hoof, in one version a single finger grows further away from the others as it's nail turn into a shape of a hoof, that version is a little too grotesque for me. Another version has a person's fingers of a single hand merge together as the nails combine and form a hoof around the merged hand. There's more versions that I like to explain, but I think it's for the best that you try to come up with your own method.
Hindlegs: I'm going to get this out of the way right now PONIES DON'T HAVE BACKWARDS KNEES if you take a look at this drawing tutorial of the third pony sketch with the joints in the top left corner, you'll see the first two back leg joints are actually the thigh and the knee, the second to third joints is actually shin, and the 3rd and 4th joint is actually the foot itself. Basically the round part of the pony's hind legs is the thigh and knee and the leg that touches the ground is the entire foot. When a person is turning into a pony that means their feet and shins literally trade places with each other.

I think that's everything that I know so far that I can help you with. It took me roughly 3 hours to type all of this down, but I hope that my comment actually helps you in some way though.

601907
Question: Do you ever get a notice that someone made a comment on your forum or is the only notice you got from this forum is my direct reply to you?

603530 Eh... You are the only one....
Yuppers...

602334 Hmm, only brushed the comment, and I gotta get to school soon, so I will provide a basic response in the meantime to hold you over while I formulate a more proper response. I'll admit, I have a weakness for TF as a fetish, and so it comes into it's own element here. However, since you did point this out, I am thinking of actually stretching that out as a character developed plot detail.

Octavia is a refined individual, correct?
If she still retained most of her base personality in pony form,
I think it would make good psychological material for Octavia to lament and
cry over, with Vinyl covering for her the entire way. A shame if you will.

Oh it will help indeed dude, you have my thanks.
I might ask for you assistance in the future.
Be ready. Until then, gotta be at school.

602334Give me an example scene on how you would write it.
Simply saying that the hand morphs into a hoof isn't gonna cut it here.

604898
That's true but there's a couple of things that I need clarifying before I start: First off since I don't know exactly how the characters are portrayed here, is it alright that any lines that I would have given Vinly and Octavia will just be "line"? Second off, I'm not exactly good with painful TFs so bear with me on that. Finally, Octavia is poisoned by the food right? Is it okay that I start from what you wrote from your first post?

604923 Sure. Give your own spin on it if you need to.
Hell, go create or use your own version of them if it helps.
Yes, poisoned by food.

And if you don't mind, I might need your help as a co-author on this.

604948
... I don't think I can help you with this area, I'm... not too dependable. :( But I will try to help you on this, so without further ado here's my attempt at writing the transformation sequence even if it could take me another 3 hours and more (Also there's difference between TF fans and TF Fetishists, just like there's a difference between regular bronies and cloppers):

Ugh... I am starting to feel dizzy Vinyl. I-I can't... Ugh...” Octavia slumped off the chair.

“Tavi!” Vinyl yelled in alarm, quickly rushing to the cellist side.

“Augh- it hurts Vinyl. M-my chest-, it feels like its on fire.”

SCRAP FOR LATER USE

“Something in the food... Octavia got that cake unsigned, that would mean...” She paused as she began to fully realize the ramifications of what was happening. “-then that would mean...”

“V-Viynl, I can't breathe.”
[Okay this is where I'll be Starting]
Octavia gasps to her marefriend falls to the floor on her side as she started shivering like an earthquake while clutching her stomach. The cellist's body started to shrink and round out into a simple shape losing her prominent feminine features. Vinyl gasps in horror as she witness the breasts of her friend is shrinks away into her body, her clothes slowly loosening up around the changing human.

"[line]" Vinyl says as tears begins to creep up in the corner of eyes.

"[line]" Octavia says weakly as her body becomes more unfamiliar with her.

Just past the waistline of Octavia's shirt, Vinyl witness grey fur sprouting from her human friend's skin like grass sweeping across the meadow from the wind. Just as the fur grows over the cellist's lower back, she feels a stinging pain as a black tail pops and flows out of it pushing the pants out of the way until stopping at a length similar to her own legs. As the fur rushes over her friend's thighs, Vinyl sees a small magical light flashing over them. "Was, that a cutie mark?" The cellist asks Vinyl as she tries to look at it but the sudden pain of her thighs getting bigger and thicker causes her to pull back.

"Y-yes," The DJ pony stutters, unsure whether or not if she was answering her friend and lover or the further instigating the brainwashing aspect of the potion.

"Please, tell me. What does it look like?" Octavia asks through the pain as the transformation of her thighs are finishing up.

Vinyl's ears folded backwards as bit her lip in hesitation to tell her friend about what the cutie mark looks like and as if to mock her indeciveness, the transformation appears to come to a halt and is also waiting for her to answer. After looking back between the cutie mark and her friend, Vinyl finally gives her answer, "It's... a purple treble clef," she starts with a nervous chuckle, "It matches your eyes."

Octavia makes a nervous chuckle as well, "At least it's-aarrrggghhh!" The cellist screams in pain as she feels feet being converted into hindhooves. It's like they started becoming thicker through the use of some bike pump and her toes on each foot were forced to stretch and combine together to become a single solid toe.

Vinyl couldn't force herself to look away as she witness her friend's shoes bursts out into what looks like small pony legs (when compared to Vinyl) in the place of feet. Then they were quickly pulled into the changing human's pants as they slowly get bigger. The grunts and cries of pain along with the cracking of bones still echoed into the DJ Pony's ears as she still couldn't take her eyes off her changing girlfriend's legs as the shins of it were quickly getting smaller and smaller while the hindhooves. The hocks (which is the "ankle" of the pony feet) poke out of the waistline of the pants as the transformation of the hind legs of a pony slowly draws to a close. Octavia is still screaming in pain as she flips over onto her stomach, causing the DJ pony to back up. The cellist's new pony legs kicking the remains of the pants off while her new black tail flails about in panic as she feels the next horrific change taking place in her body.

Vinyl didn't know what to make of her half-pony half-human friend at the moment, making her look like a cross of some sort of pony saytr. All the DJ pony can think of is how is why did this have to happen to her friend until she called for her, "Vinyl, my arms! I can feel them changing!" Vinyl's mind snaps back into reality and quickly trots over to her fallen friend whose arms are outstretched in front of her.

Using her magic to pull the sleeves back a little, Vinyl only made it just in time to see her friend's hands getting covered in grey fur like a wave of water washing over it. The changes seem to stop at the moment as Vinyl and Octavia looks at her fur covered hands like she was wearing grey mittens. Silently both the human and pony smile at each other in the tiniest bit of the hope that the transformation would be incomplete after several seconds of nothing happening, that this only as far as the transformation can go, maybe the transformation will revert the human cellist back to normal since it couldn't finish the job. But alas, it was only the eye in the storm. Octavia suddenly grits her teeth in pain has her fingers of each hand were forcibally merging together to become the front end of a grey hoof. Then her hooves started become thicker and more rounder that her arms look like they were simply furry poles. Then the hooves started stretching further away from the original position of her hands until they finally become the forelegs of a pony.

"I'm sorry," were the words that came out of Vinyl's mouth. She closes her eyes as she couldn't help but think that if she hadn't become a couple with Octavia, if she hadn't become friends with her, heck, if the ponies and Equestria hadn't appear on Earth in the first place, this would never happened to most precious being in her life.

"It's not your fault," Octavia's voice croaked. Vinyl's eyes open to see Octavia's neck slowly thickening and elonging, "Remember when [line]" Octavia asks through her slowly expanding pony neck weakly.

"Yeah, that was about [line]" Vinyl starts,

"[line]" The changing human cuts her off her neck is half way there from a pony neck, "It wasn't your fault back then, and it is not your fault right now," Octavia finishes as fur cover neck is now a pony neck, leaving the only thing left to transform is her head.

The words struck the DJ pony's heart so strong that it knocked her out of her helplessness and despair, "Thanks 'Tavi," the pony says after wiping away the tears she had before Octavia's speech. Vinyl took one last look at Octavia's smiling human face with her own smile. But then Vinyl put on a look of determination as she notice not only were Ocatavia's ears being pulled into pony shape at the moment, she notice the tired look in her eyes, Octavia is about to lose consciousness. She had only a few rumors about it, but if what they say about the "conversion dream" is true, then Vinly knew she can't let that happen for the ever growing fear that once she wakes up after this, there's a chance that she'll probably won't be the same Octavia again.

Desparetley DJ pony grabs the transforming cellist with her white hooves, whose ears are now pony like and stick up at the sides of her hair. "Octi, look at me. Please look at me," once again the transformation takes a dramatic turn and it slowing down it's process. Vinyl wasn't sure if it was her friend's will stopping the change or the changes own sadistic move. Octavia stares into Vinyl's large red eyes [her eyes are red in this story, right?] with a tired look in her eyes the grey fur slowly creeping around her head. "Come on 'Tavi, don't fall asleep. You can fight this I know you can," Vinyl pleads to her.

"Ii.t.. I'll, try," Octavia says weakly, the grey fur seems to slow down even more.

"Come on Octi remember that time when [line]" Octavia quitely nods as Vinyl continues, "You didn't give up then." Octavia wanted to comment on her part of the memory but was interrupted when her head starts becoming rounder into a pony shape. Vinyl feels that she was close she can't let her girlfriend fall asleep on her now. "Octi remember our first Chirstmas together?" Vinyl asks.

"And you had to meet my familly, which turned out to better than I expected. I didn't expect, everyone would like your music," Octavia says with a smirk not noticing that her eyes were getting bigger now that the grey fur finished covering them. Her purple pupils now becoming more defined and the highlights becoming more noticable even if Octavia's eyes were half closed from fatigue.

If Vinyl was still paralyzed with horror she would have stop talking and look at the changes going further, but instead she continues the conversation, "C-come on, not every song I played there had dubstep in it. You know I played a couple of your favorites also."

"... Yeah... That's true..." Octavia said as her fatigue returning to her with a vengence as her mouth and nose pulls into a muzzle completing her transformation into a pony.

"'Tavi, no, you have to stay with me." Vinyl cries out to the newly formed pony whose large eyes are beginning to close now.

"I'm, sorry, I... just can't..." With that, Octavia falls unconscious while Vinyl desparetly tries to wake up. But the DJ pony has no choice but to wait for the newfoal pony to wake up and hope that she is still the same...

That's it, I didn't think it would take me this long to write it out but that's what a long transformation sequence is like. Unfortunately, my creative juices started to run dry in the end and I'm sorry for being so strange with taking your word of putting on a different spin on the couple halfway through the example, I guess there were some things that needed to be said even if the emotion was done half heartedly. It's just that it didn't feel right, writing lines for your Vinyl and Octavia when they have their own lines and story to be told. You also know how the couple lives better than I do so I wasn't sure if I was right writing about a past experience they have. Anyway I hope you can understand about one of the ways of writing a transformation sequence and also I'm reconsidering about being your co-author now but maybe if I stick to one thing, which is the transformations I could help out a little in that area. But I don't think this story needs anymore transformations does it?

It may help to think about the individual steps and how they happen before you can pick out which momentary snapshots are essential in making the change flow for the reader, like I hopefully succeeded with in chapter one of "Space Ponies".

Here's pony changes as I understand them, as opposed to flash-of-light *poof* changes, aside from giving the poor slob time to shrug off any human armor or equipment that could really hurt badly with a new shape.

One thing to consider is size. are the humans essentiailly the same size as their pony forms? one-to-one ratio? A little smaller or bigger?
I work with IRL ponies, specifically Miniature Horses and American Shetlands and I worked this info into my main Pony Tale whenever humans such as my hero find themselves in Equestria.
They stand about 22"-30" at the shoulders but with some measuring, I find our little ladies and gentlecolts would be roughly human size if they could stand upright.
However their body proportions would wreck standard human clothing if it suddenly appeared on them. -Particularly the barrel chests of stallions and thick, angular hocks.
The exaggerated features of MLP Ponies magnify this considerably.

Bras and blouses would pop buttons and clasps, then tear at the seams if a woman turned into Miss Quake from the Ponyville Day Spa.

If they became a normal, slightly built mare, the shoulder seams might tear, then the back seam as their new legs pull downward on the arm holes (wing buds stretching and poking through fabric then rapidly growing and shredding the cloth might be a nice touch.) and end up with them wriggling out of their loose bra and shredded blouses.

Oh yes, a fave of mine; Tails! We all have tails, but a tiny bunch of fused bones an inch long and hidden inside, serving as one of the anchors for our colon muscles. unless this pushes out above the waistband, you might have this strong nub of bone and flesh pushing on, then through, panties and swelling out into a 6" or 7" tapered, fleshy tail before the hair comes in, long and lush.

As for heads, will it feel like their heads are swelling? their vision blurring up while their eyes change and grow? The ears twitching and burning as they grow larger and gain muscles? Will their hearing drop out for a few moments as the ears shift upward and the nerves and working parts shift and move around?
Will their teeth and sinuses ache as their faces push out into an abbreviated snout and teeth reshape to fit? Guys will probably have the worse end of that with their thicker, longer snoots.

As for the hooves, the unique physiology shown in-show does allow for a change I usually dont prefer to see in horse TFs, hands and fingers merging into a single mass. they constantly shift from using it like a leg to using it like an arm, with the hoof in the hand position.

Feet, legs and hips will be really spectacular as the angular hock seen on horses and MLPs are the heel on humans. the toe area swelling into a hoof while the rest of the foot stretches, the calf area compacting into the gaskin while the thighs and hips merge together into rump and flanks, likely splitting any pant legs or waistbands left fastened. Skirts will probably be mostly intact other than the snaps at the waist.
Celestia help you if you still have a belt on, and hope its a cheap belt...

I hope some of these bits and pieces help...