Though I think that writing in dialect is typically something best left up to the likes of Mark Twain and Toni Morrison, I do occasionally think about the way people say things.
Accents fascinate me, though the range of ones that I can imitate is limited. Irish, sure, but not such that would fool anybody from Ireland. Same with Southern. Once upon a time, I had a CD given to me by a friend that was theatre material, coaching you how to appropriately do a British accent. I was all right with that for awhile, when I still knew where the CD was. I also managed a "pirate" accent for a little while, after watching the first Pirates of the Caribbean movie far too many times (if there is such a thing, though the first is the best of the series I feel.
But anyway. When I'm reading a novel or a short story, somebody has to really hit that voice right if they're going to try and write it in dialect. I'm not talking about the occasional "ain't". I mean full on shortening of words, anastrophe, whole nine. It can be garish and irritating, or it can be pitch perfect. I'm not sure where the balance is, really, and mostly avoid it. That isn't to say my characters are always grammatically correct; I do still try to phrase things the way people say them. I just don't do spelling gymnastics in an effort to make you understand how they're saying what they're saying.
The way people say different words definitely interests me. Sometimes I hear it in a different way and keep that with me in my mind, turning it over like a found coin. Sometimes I hear a way that's familiar, and I realize that's how I've heard it, or say it myself, but hadn't become aware until I heard if from a stranger's mouth.
Do you enunciate "twenty"? Or do you say "twenny"? Do you say "pocketbook" (if you even use the word "pocketbook") or do you say "pockabook"?
Of course, there are funny ones. "Fiddy" instead of "fifty". "Ermahgerd" instead of "Oh My God".