"All I'm writing is just what I feel, that's all. I just keep it almost naked. And probably the words are so bland." - Jimi Hendrix
One of the challenges in writing fiction, whether or not you decide to make your setting a MAJOR THING in the story, is making your readers feel at home. I've already gone over your personal writing style and making your readers feel at home. Today, I'll get into something that can be more of a technical aspect. I use that term very loosely, because this part of writing fiction (or even non-fiction) is not much dependent on mechanics. You can't memorize a method for it or figure out how to do it from a textbook. It must simply be mastered. Want to know what this all-important thing is?
Writing like you speak.
Not so hard, right? I mean, it seems pretty easy. Just write stuff like you and everyone you know says stuff. Easy stuff. Slang, here you come. Colloquialisms abound. Awesome.
Here's why. Ever read a transcript?
Yeah. Writing a sentence exactly how someone says it, every time, is as bad as trying to make your random hilarious true story into a scene in a novel. No one is going to believe it. Case in point: any time anyone tries to give characters a "Southern accent." I have read the word "gwine" too many times in my life. I still don't know how you're supposed to pronounce it. (Like swine, maybe? I'm really not sure.) I know it means "going" and is supposed to be Southern (or just Old Person Southern), but it gets on my nerves. A lot. It's a really bad way to have a character (old or young) talk because it's a good indicator that a) you don't know what you're doing and b) you've never been out the house or flipped on the TV. Same goes if you insert some New York or Boston or California slang stereotypes and try to phonetically indicate how people in a certain place speak. Unless you are making a movie and are the Coen brothers, it will not work.
So your real challenge is to make your writing, prose or dialogue, seem as though it is actually someone speaking. Nicholas Sparks is pretty good at this. Honestly, though I am from North Carolina, I wouldn't speak like he writes, but somehow the guy manages to convey a conversational tone without it actually being anything from a conversation.
So how can you do the same? Well...practice. Read books that feature that local flavor feel. And practice some more. Bounce your ideas off willing friends. The method and time are different for everyone, and it may take some work before you find that conversational groove for your fiction. But once you do, it will be all worth it.