I'm assuming you're not just writing the character so you'll have the challenge of a phonetic accent, correct?

Speaking from experience in the POTC fandom...phonetic accents are very, very hard to do well. I see it all the time, even in otherwise well-written fics, where poor Jack Sparrow ends up sounding like anything from street teenager to Southern to Scottish. Yes, Scottish.

On that occasion, Potcsues had some mightily helpful advice for prospective accent-writers:

Hasunoutena: Is dialogue always written like that in PotC fics? Because after I read the snippets of that fic, I can't get the Scottish accent out of my head. I'm sure that wasn't the intention.

Potcsues: Well, not always.

Some people just don't feel like bothering with anyone having an accent at all and get caught up in making everyone speak "proper" English. Unfortunately, to make someone speak proper English one needs to have paid attention in an English class at least a few times in the course of their lifetime, so that never turns out well either.

It's very rare that someone just alludes to an accent, like people who know what the **** they're doing do when writing accents in fiction.

As for me, I wouldn't say that phonetic accents can't ever be written well under any circumstances, but I wouldn't advise anyone to try it without a strong background in linguistics or at least a few years listening to the accent on a regular basis. In addition to alluding to an accent, what will help distinguish your character's speech will be the word choices and colloquial expressions that he uses, which is usually more than enough for the readers to get the idea.

Ќ—Araeph

Take refuge in audacity. Make this character the embodiment of all the positive stereotypes (e.g. always friendly, boisterously happy, likes loud and silly traditional drinking songs) and then make their accent completely ridiculous. If you're going to be stereotypical, and with a phoneticised accent you are whatever you try to do (consider any foreign Bond villain or the Dobermann from Up), the least you can do is be nice. =]

The Cajun Accent is hard to replicate without sounding offensive, especially if you have not heard it properly. Living in Louisiana, I have heard it, but in order to be most helpful I would like to know a little bit more. You say near New Orleans, do you mean like a suburb of New Orleans? Do you mean Baton Rouge? Or do you mean Ascension Parish (Deep Bayou)? Or do you Atchafalaya Basin (Swamp People from History Channel)? There are slight differences in all of those accents, and all can be considered Cajun and near New Orleans.

But for general advice I recommend three things. First Diction should be your first choice, a phonetic Cajun accent runs the risk of becoming in comprehensible. Second, and this is in most cases going to be a must, throw in a smattering of French. Things like 'mon ami' or 'laissez les bon temps rouler' (Let the good times role) (Useful in certain circumstances), 'cher/cheri' is another one. And finally as a good generic guide in my opinion, look at Gambit from X-Men (Comics or Original 1990's Cartoon). He works as a pretty good template.

Usually with Irish English and Cockney accent...

Still, have all my help, dude:

Wikipedia article on Cajun English

General accent writing tips