It's tricky to use dialect well when writing fiction. In earlier times (think Mark Twain) writers could get away with all kinds of deliberate misspellings and other obvious tactics to indicate dialect, especially in dialogue. For several decades now, editors have disliked that approach for a variety of reasons, including the view that deliberately writing poor grammar or spelling for a character's dialogue can seem insulting to the character, or the character's ethnicity.
Still, dialect exists and if you're writing about a part of the world in which it's spoken, you have to address the challenge head-on. I like the approach Dead Man Breathing, one of our honorable mentions in issue #17, uses: it italicizes the dialect and isn't afraid to explain its meaning when the meaning is not obvious in context. Yet it recognizes readers will get most of it on their own. However, the dialect doesn't sneak into the narration; only the character's thoughts use dialect.
Contrast that approach to the one taken by Larry Brown in his award-winning story Kubuku Rides (This Is It). (I hate that title, by the way. I'll explain why I think the title is the worst short story title I've ever seen next time.) This time, the point is how Brown integrates dialect into the narration. Here are its opening lines:
Angel hear the back door slam. It Alan, in from work. She start to hide the glass and then she don't hide the glass, he got a nose like a bloodhound and gonna smell it anyway, so she just keep sitting on the couch.
His other stories I've read don't use that dialect; it was something that worked well for one particular story, so he used it. I think it provides a great deal of atmosphere and does so without insulting or making caricatures out of the characters.
So there are at least two effective ways to write dialect when you have to. Pick the one that works best for your story's purpose.