Common Issues and How to Avoid Them · 10:11am Feb 6th, 2017
A collection of errors, advices mostly for beginners and something more I often point out--putting this up here just for reference. Still, feel free to read and share your own experience!
1) Character descriptions
He had black coat, yellow and green and cyan mane and tail, his left eye was vivid crimson red and the right was deep purple. His wings and hooves were light blue with white spots and his cutie mark was that of red and yellow striped spider sitting on Spike's head. The cutie mark was too on his armor made of platinum, gold, diamonds, rubies and emeralds. He liked knitting and curling.
Uh... what? Were his eyes yellow and cyan, which one was which...? Screw it, I'll just remember him as the pegasus guy! Reaction of many readers-- there is too much information shoved to them at once. In the end, they remember nothing.
What to do with it? Mention just a few things at once. Coat and armor the first time for example. When it fits, add eyes or mane - Maybe it's a new day and they shimmer in the morning sun. Also, don't describe in the fashion of shopping list (eggs, milk, apples...) but instead spend at least a sentence on each feature. You can also try and include some personality trait--happy eyes for example.
However, even the shopping list method can sometimes come in handy. For example imagine you have a character that witnessed a crime. Then it's completely okay if the pony says, 'The burglar was a burly stallion of short build, had a tan coat, dark beard and a green hat.' The character didn't notice more, so they just sum it up. But as a writer, try to drop more explanation.
Another side is the description of canon characters.
Everyone on this site knows that Twilight has purple coat, purple eyes and two magenta streaks in her mane. You are just wasting space and time on that description. As long as your version of Twilight doesn't wear firefighter's jumpsuit all day long and there isn't a green tentacle covered in colorful feathers instead of her horn, you can leave her description out.
Again if you wish to have her description, do so, but please not in the 'shopping list' fashion as described above.
2) Tags
This sad random comedy slice-of-life drama story takes place in sci-fi alternate universe filled with dark gore-y horror and sex. And apparently there is an anthro human from some movie it's crossover with.
That's how the hailstorm of tags on stories usually looks like. Which genre is the story in then? What should the readers expect? They can be easily disappointed because they started reading, expecting a good slice-of-life. Sadly, it was just a minor aspect.
Always try to use up to 3 tags + Sex, Gore, Alternate Universe. Think about what are the main aspects of the story. The fact Luna has freckles in the story doesn't make it an AU, just like Twilight cutting herself with paper doesn't make the whole story filled with gore.
3) Check, check, check...
When you finish a story, you want it to be the best, right? Getting a pre-reader, beta reader, editor, proofreader... (whatever other titles travel around the site) is not a shame. Actually, all the "great and powerful" writers do it too and have many of them, only to ensure their story is good. No matter how many times you read through your story, there will still be a few errors escaping your eyes. That happens to us all. Another pair of eyes can see them easily. So pick out someone's eyes and throw them on the screen 
However, no matter if you persuaded someone to read your work, you should always check it after yourself. Read it carefully as many times as possible, use some spelling checking tools, look up things you are unsure of. Either it's the only check-up the story will get or you can ease your helper's work, letting them focus on the remaining issues.
Also, very common mistakes are made in direct speech. I don't want to delve too much in it here, so just a little advice. Look into any real book, it should be okay here. If that's too old fashioned, you are using the internet just now. Look up the rules and examples.
4) Long sentences that sound like Pinkie talking and usually become long as a paragraph because you want to finally get all the ideas from your head and move on to eat that yummy lunch waiting on you in the other room the one you were looking forward since Friday so you just add and add sentences in a snowball effect and in the end nobody knows how did the sentence start.
That's quite an example... when you have to read it twice (or more times) to catch all the information, it's bad. Try to split it into a bunch of shorter and simpler sentences.
5) This happened, then this and then this. Suddenly, there was a cutie mark!
Sigh... typical description of what happened. However, it's just a mere statement. What are you trying to accomplish is to make the reader track the story, get hooked, feel like he/she is in the middle of the action. Describe in details what's going on. Build up the tension!
Don't rush some parts because you have the most epic scene waiting for you. If you rush the scenes before it, nobody will read further than that. Thus, there will be nobody to enjoy the most epic chapter you worked so hard on.
6) Repetition and verbs
"..." she said.
"...?" I said.
"...!!!" she said.
"*@/;?!" I said.
That looks like an ordinary smalltalk of two teenage girls... But mostly, it's boring and repetitive. Said, said, said...
You can replace them with stated or remarked for example. However, some people are not fans of that, because then you are just a step away from this:
"I'm sorry," he apologized.
Everyone knows that's an apology, no need to point it out. Instead, you can use the verb to convey the emotion:
"I'm sorry," he whispered.
The character is feeling deeply sorry. Maybe he's shy and timid.
"I'm sorry," he retorted.
The character is quite brash and probably not really sorry.
"I'm sorry," he groaned.
The character is mostly bored and annoyed by the fact he has to apologize.
See? With "said", the reader wouldn't know a thing about the character. When you use other verbs, you can convey more. Although, said can be and often is used, because everyone just needs to simply 'say something'. But it should never be the only verb you'll use.
Of course, 'said/say' isn't the only case of repetition, but it's a really common one. Another case could be repetition of names. Really, seeing the name Applejack for a hundredth time in one paragraph is not pleasant. Remember to use synonyms or pronouns so the reader doesn't get fed up with certain words. In the case of Applejack, it could be simply she, the mare or the cow pony.
7) Tenses
"Hello Cipactli!" greeted the Tatzlwurm.
"Hola." The crocodile-toad sighs.
"What? You look sad." The worm creature raises his chin up with a mouth-tentacle.
"Have you already met this Daring Do pony?" Cipactli asked.
Okay, writing these monsters is really weird... See those underlined verbs? Two are written in the present simple tense whilst two are in the past simple tense. This shouldn't happen. There must be just one of them, doesn't matter which.
8) Logic and consistency
(Random stories and some comedies don't have to abide this.)
Think about what are you writing. You can't have Shining Armor trapped by cave-in in the mines of Maretania, only to be saved by a sea serpent that just decided to go for a walk despite having a broken leg. Just like you can't have a character saying she is afraid of water and being an excellent swimmer in the next chapter. Of course, if you have the character then explain that she loved water until something dreadful happened, it justified and not a mistake.
Remember to think, think, think and reason, reason, reason. "And sometimes use the artistic license!" 
"Yeah, thank you Pinkie, I forget about that."
Stories about Pinkie or Discord don't have to really abide this rule... Still, don't sacrifice their character to irrationality, they have their own logic. That's why most people find them hard to write properly.
9) Descriptions of surroundings and transitions
We sit in the train car, bumping on the aged sleepers across Appleloosa Desert.
"I think I'm gonna take a nap," my companion yawns, plodding to the sleeping car."Hello my little ponies, what brings you here?" Princess Celestia leans forward, sitting on her throne.
What?! How? They were in Appleloosa one moment and now in Canterlot! There needs to be a line break, like one of these:
***
-----
But mostly, there needs to be some description signaling the transition. Not just The next morning... or Next morning in Canterlot... but also a few words about the surroundings. The reader can't see inside your head, be concrete!
10) Don't rush it
Part of rushing already explained under 5). However, remember this is just your hobby. Forcing yourself some insane deadlines only to please the readers is a nonsense. The result will be full of typos, half-thought sentences and such. In the end, the readers will be far more happy to wait one more week, but have a pristine new chapter. The intelligent people (audience you should aim for) can understand that you have something important going on in your real life and you can't waste your time shipping colorful horses and not-so-colorful griffons.
Also, don't write when exhausted, sleepless, intoxicated, enraged, crying with joy... whatever. These states cloud your mind and again, the written part will be disastrous spelling and grammar-wise.
11) Don't write for fame
Great seeing others having thousands of followers, selling their stories and getting tons of compliments, isn't it?
Don't write just because you want all that too. Write because you enjoy it. If someone else enjoys the story, welcome them aboard and take it as a bonus that your story entertained them.
If you don't comprehend this, the fact your story didn't get hundreds of views the first day will destroy you and your will to continue.
12) Reacting to feedback
Despite not being featured on the main page, your story will get some comments in time. Right reaction to them can get you more readers for this or other stories or you can even make a new friend. Let's see which kind of commenters you can meet:
A) You suck you Celestia-chewed cake! First! Is that yellow alicorn on cover art your OC?
Trolls. Better not reply to them. Well, the last one could be considered case by case basis.
B) Great chapter! Tracking!
Thank these people. You can even try to engage in a conversation about the story.
C) The story is terrible, there are so many mistakes and you don't know how to write!
This might be just a troll hate. However, be polite to that person and ask if they could mention direct examples of the mistakes and why they think the story is terrible.
D)This was an enjoyable chapter, I like your portrayal of Gilda. Be aware that you have there slight mishap between your and you're. Also, your Princess Celestia speaks like a mobster, was that intentional?
This is the most precious comment you can get - constructive crititique. The person did not only take time to read and comment, but they also try to help you. Politely thank them, fix the obvious errors and elaborate with the person on the rest. They might be critical - sometimes even a little too much - but as long as their provide sane ideas, keep them around.
E) This story would be good if you didn't ship Mayor Mare with a Diamond Dog. Ship her with Steven Magnet instead!
Remember, this story is yours (and maybe your co-writer's) and yours alone. You are the one who wrote it and who will receive all the love. Don't let anybody tell you what crucial part you should change. However, if someone calmly explains that what slight detail you have there doesn't make sense, listen to them and think about it yourself. However, what was shown above isn't that case. Thank that person and politely explain that you can't really do anything about that.
One more thing before we end this; you have learned a few rules. However, I'd be lying if I said you should hold to them no matter what. Take part 4 - long confusing sentences for example.
Is having a whole story written like that an issue? Yes it is. Is writing some hyperactive character like that for a comic relief an issue? No, it isn't. It instead helps to add life to that character. Those rules could be exploited for the plot sometimes, but just sometimes.
Many thanks to MV for suggestions and refining my statements.
Signing off
-Ever
I can see some of these stuff is MY issues
Nevertheless, I'll keep them in mind 
So sorry though for MY nitflicks
4411191 No, not anymore. Besides, you already had a readable style, these are far worse and I see them commonly around the site
Shh, nitpicking means you point out every small detail, not make mistakes.
4411196 Aww
and opps! 
My bad and personal error! 
Interesting read though some of those are quite common rules to be found on this site alone. Of course people still make same mistakes.
About tags though I sort of suspect people pile up 6 tags just so their story would be found by more tag searches (the cluster of crazy tags makes me think twice if I want to read at all a story). That or they really think that for example romance is a thing they must have if they are writing a big story because of course all big stories have hero falling in love. Though that doesn't make story a romance genre it is just a story that has romance in it and people do not understand what tagging genre means.
4450707 Thank you for stopping by
I use this blog mostly as a storage for advice that I can refer to if needed during editing. And of course many of them can be found around the site - it would be bad if I was the only one talking about general rules, after all 
Yeah, I mostly try to avoid those stories burdened with so many tags. I reckon it's exactly as you said; need to have more tags for more publicity and also to pin down every little tidbit of different genre.
ok.....
BWAHAHAHAHAHAHAHAHAHAHAHAHA
I'd honestly like to see what I write when I'm drunk
4582723
Well, if you want to write bizzare random stories, go ahead
4582958
Except I won't get drunk because I'm responsible.