While Applejack is not the only one of the Mane 6 to have a noticeable accent like Rarity, she tends to say common words in a different enough way. This also applies to the rest of the Apple family living on the farm. Although it’s least noticeable with Big Mac just due to how little he speaks outside of a few special cases. But even saying “eeyup” is tied to a southern accent.

How to handle these accents in writing? You could just write the words out normally, which I personally think is the least interesting way to go about it. I guess you could lay it on thick by varying degrees, although how far before it could become annoying is up in the air. How does official media handle this like FiM with subtitles or comic books?

Furthermore, the varying degrees of the southern accent could apply differently from Apple Bloom to Granny Smith in fan works. I haven’t written any accent differences in my writing between the 4 main members of the Apple family. And finally, the characters inner thoughts could lack the accent entirely. Like say a first-person Applejack story where her wording is written normally except when she speaks out loud.

7968058
I think the best way is to actually spell the words as they sound from AJ:
- "I never thought" > "Ah never thought"
- "That's my favorite" > That's mah favorite"

7968069
"I never thought" > "Never figgered"
- "That's my favorite" > That's m'favorite"

Don't use a club if a feather-duster can do just as well.

7968058 I'll just throw up this wall of text here:
Cut off the 'g' in '-ing' words and replace it with an apostrophe (wantin').

Nelly, Sally, Partner

Y'all = "you all," never "you."

Ya = you

Ah = I

As for the rest, just takin' out a letter or two won't hurt nothin', particularity the "g."

"Ah sure as sugar plumb reckon y'all are!" Applejack chuckled. "Want ta see if y'all can get a cutie mark buckin' apples?"

"Mah name is Applejack and ah tend ta talk lyke this. Ah reckon' it's because some authors think readers can't 'member ah got me an obnoxious southern accent" 

"Dangit, Rarity! When are you ever gonna get it through yer thick noggin' that I love you?!"

Replace 'you' with 'ya' but only when it'd be pronounced 'ya'.

"Howdy there! What bings ya to tha' farm?"

 When in doubt, go with 'you'. Ya might say somethin' like this, but there's plenty of times ya might not. Figuring out when is up to you. (Intention you there, since it'd sound hella weird to say 'ya' out loud in that last part).

Add some common grammatical inaccuracies. Me and my friends did this (instead of my friends and I). Could of, would of, should of (instead of could have, etc.) Better yet, coulda. In fact, you can combine words like that a lot. I mighta heard you're tellin' an Apple story.

Double negatives. Ain't nobody gonna tell me the Apples don't use double negatives.

Y'all is a contraction of 'you' and 'all'. The apostrophe goes after the 'y' and before the 'a'. Do not write ya'll. (But do write y'all, howdy, mite, and partner freely!)

Double contractions are cool. Y'all'd love to try some of my family's cider!

Try to imagine what it’s like growin’ up not knowin’ yer parents. Do ya really want that for Spike?

Ah'm going to tell you the honest truth. Ah don't know.

How ya doin', sis?

nothin' much. Work got slow at th' marketplace

An' RD thought it'd be funny t' have a mini thunderstorm on mah stand, so Ah headed home. 

What're ya up t'? You an' yer friends ain't gettin' in trouble, are ya?! (Don't even try t' say ya don't git yerselves in hassles.)

Well, it sure is fancy-lookin' an' Ah'm surprised y'all managed t' pull this off, but yeah, Ah like it. S'pretty nifty. 

Mind mah askin' who Applebuck is?

...he ain't yer coltfriend, is he?!

Ah don't want mah 'lil sis growin' up too fast.

Ah reckon Ah dunno any ponies by th' names

she's a nice gal.

Comes ov'r fer dinner from time t' time

we decided t' let 'em play.

If we start workin' at dawn, I reckon we should get the stage done lickety split.

Why are y'all treatin' me like I'm dense? I know what's goin' on, I ain't dumb.

You're makin' as much sense as a jackrabbit in rollerskates. Nah, even jackrabbits in rollarskates would make better sense then you right now.

What in tarnation

Y’all

don’t trust ya.

Ah’m beginning to

‘round

Ah recon

an’ all

http://www.fimfiction.net/group/50/the-writers-group/thread/113389/help-with-applejack-dialog
http://www.fimfiction.net/group/50/the-writers-group/thread/176525/cracking-ajs-dialect
https://www.fimfiction.net/group/50/the-writers-group/thread/476883/how-to-translate-into-applejack-accent
https://www.fimfiction.net/group/50/the-writers-group/thread/309962/how-do-you-write-a-good-accent-for-the-apples
https://www.fimfiction.net/group/50/the-writers-group/thread/320149/writing-in-applejacks-accent
https://lingojam.com/CowboyTalkTranslator

I think it's a thick Texan or Southern or something

7968194
As someone who is a native speaker of and fluent in Southernese, I can say that y'all is both singular and plural. Ya can also be singular and plural. It all depends on context.

The most common Southern farewell is "Y'all come back now, ya heah?" That can be said to a single person or to a group of people.

7968058
The South is full of wild, weird and wacky accents and dialects. Some of them are their own distinct languages, like Gullah or Louisiana Creole French.

One of the best ways to learn how to write a Southern dialects is to listen to someone who is from there and make some notes on how they talk and what phrases they use.

7968194
Whoa, that is a lot of stuff. And it would seem this topic came up a few times from the links given. Perhaps I should check out The Writers' Group. Looks like they really focus on wanting to write great stories. I haven't written the Apples accent quite as thick yet, it's the sort of thing I just need to keep learning as I continue to read and rarely, write. It certainly adds character which is why I want to include it when possible. Which I wonder if their thoughts or first person narrating should lack the accent like going instead of goin'. But then there's entire words and sentence structure that comes from their accent so I guess their thoughts would have a lot in common with their speech.