Of all the mane(and human) 6/7, she's probably the most difficult in terms of consistency. I get the type of character she is but from what I've seen, she's written in a number of ways. I guess the main question is is there any one way to write her? I would love your option on the matter.

7197117
First and foremost, there is no one way to write a character. In the end it depends on your style and the traits you need to emphasize or develop for the story you have in mind.

A better question would be how to not write her, since that's where most people fail. Keep in mind that Pinkie (and similar characters, such as Discord) are not an easy deus ex maxina device or a plain chatterbox spouting random nonsense all the time. These characters have their own inner logic that only they understand, and you have to respect that. If you go ahead and use such a character however you wish, it's likely going to backfire. Besides some badly handed fourth-wall breaks, a very common thing you may see is Pinkie blurting out something important, just "'cause she's the weird and stupid one". Not only is that awfully cheap, but it also fully undermines the character's potential.

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There is no one way to write a character, darling. Everfree is right.

How you write character depends on how you understand character and what the role for a character is. It's not same when Pinkie is a main character and we see things from her perspective and when someone else observes Pinkie. The wrong way is to forget that Pinkie is a character and not a check list of jokes.

Now, I can't tell you how to write a character. I can only suggest getting in character's head and ask yourself what would Pinkie do. Also unique thing about fanfiction is that you can always watch the show for reference material.

I'd watch some Pinkie Pie Clips from the show to analyze her behavoir. In some way I can get in this character, and don't fear to try new things out. Pinkie is also more just a random comic relief, and I won't use her always as such. She's pretty creative and thinks mostly with her heart or the stomach. On the other hand there is Twilight, who thinks always with logic. "Feeling Pinkie Keen" is for example a very good episode describing both characters.

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Think random thoughts. Like Bobobo-bo bo-bobo and Wayside

Effervescent. If the personality feels right, then you’re on target. Pinkie Pie is generally effervescent.

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Keep in mind that Pinkie (and similar characters, such as Discord) are not an easy deus ex maxina device or a plain chatterbox spouting random nonsense all the time.

Unless you're writing a Random, Comedy story, then it works too. It's really the context of the story that decides whether the behavior of the character works or not.

7197117
I do agree that there is no right way to write Pinkie, but I do believe that there is one rule that one should follow if they want to write the best Pinkie possible. Rule: If Pinkie Pie does something that will affect another pony, there can't be any ill intent behind it (unless they either break a Pinkie Promise, are a villain, or [sometimes in RD's case] take things to far).

I know that seems like a basic rule, but I think this is a essential part of her character. Pinkie isn't petty, and she knows everyone's limit's (to an extent). She can be overbearing, but that's why everypony likes her, she cares about them.

As EverfreePony said,

Besides some badly handed fourth-wall breaks, a very common thing you may see is Pinkie blurting out something important, just "'cause she's the weird and stupid one".

In comedies and parodies, this makes sense. In other stories, not so much. Honestly, it hurts me to see her written this way. If she is written well, she'd arguably be the best character in any story, in my honest opinion.

However, if Pinkie was written not following the rule, the only way that I could see it be justified is by the potential threat being greater than her reaction (that or a similar event to Pinkielovania.)

Some important points to remember.

Personality

• She's an altruist - she wants everyone to be happy all the time and devotes a lot of her own time to ensuring this on a tiered basis - her close friends get the most attention, then everyone within the general area, and she deliberately avoids thinking broader than that or she'd go mad. (As she grows up she comes to realise that ponies can't be happy all the time, anymore than she can herself, but it's still very hard for her to be around a pony who isn't without meddling.)
• She has a strong tendency to assume that others likes and dislikes are the same as hers - she can overrule this in the specific by learning more about someone, but no amount of doing so will stop her making the same assumptions next time.
• She's an extreme extrovert who can be very in-your-face and will not realise it's an issue unless it's pointed out - preferably gently, because the idea that she's made someone less happy can either send her into a pitiable slump or have her double her efforts as a form of restitution.
• She's highly intelligent - arguably as much as Twilight - but you'll never find a standardised test that'll show it.
• She's usually quite trusting, but that also makes her susceptible to rumour and gossip.
• Oh, and however different they are, she really loves and respects her family.

Abilities

• Pinkie Sense - the show may forget about it most of the time, but that doesn't mean an author should. Gives short-term notice of certain kinds of event - like falling objects - within a radius not coincidentally about the size of her social one I mentioned above. Said notification is via bodily signals, so it can probably be thrown off if she's sick, and new ones take her a while to figure out (by trial and error mostly).
• She can do impossible things with spacetime - traversing distances too quickly, doubling herself briefly, and so on - as well as other affects which might seem pulled from Discord's playbook. (Not quite the same, though - for instance, I don't think she's ever created or altered a living being other than herself.) She doesn't consider these as "magic" or use them consciously - it's all just her attempting things that seem possible to her and the universe acquiescing. Notably, it can backfire on her sometimes.
• She has items stashed all over for emergencies, and can produce equipment as large as a party cannon at will from... somewhere. Asking where, or checking if she ever obtained those items in a normal fashion, is not advised.
• Making a Pinkie Promise may give her some power to tell if you're considering breaking it and intervene.
• What magic she has as an earthpony, if any, is overshadowed by the above as well as the generally subtle nature of that tribe's abilities. Given her family, it could be rock magic of some sort, but something more unique is also possible. It's also not clear to what degree her pony magic is linked to the other stuff.
• Oh, and her human self, if anyone's interested, combines at least some of the above with the power to turn sugar explosive by touch as long as she's within a few miles of her geode.

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7197664

She's highly intelligent - arguably as much as Twilight - but uou'll never find a standardised test that'll show it.

I would disagree somewhat here - Pinkie isn't smart, she's wise. Her talent isn't calculation or raw knowledge. Her talent lies in saying the right thing at the right time, or providing insight that everyone else overlooks. She's the Zen master in a koan who cuts through assumption and social structure to expose the heart of an issue.

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And I'd disagree back - wisdom would probably mean understanding other ponies a lot better than she does. She does have a unique way of looking at things, but it's backed by a fierce intelligence who would make a great scientist if the laws of physics were testably consistent in her vicinity.

7197120 I see. Thank you for the detailed explanation.

7197128 Makes sense. It highly depends on her role. Thank you.

7197130 I'll have to re-watch that ep to get a better grasp on that. Also, love the bio pic.

7197145 While a little vague, I get the general of what your're saying. Thank you.

7197193 So keeping her basic trait in mind but at the same time expanding on said trait. Thank you for your input.

7197664 That's a lot to take it. But then again, it's vital to what is needed so thank you for the detailed explanation.