Most of my stories are through the eyes of a Montana rancher, and all of the slang I use is derived from my family. I really like dialogue to sound authentic. Below, I've written examples of idioms and slang that my family uses, especially the older members. In the comments below, please offer up slang, accents, and idioms from the places you've been, but be sure to tell where you've heard them.
"I feel like I've been rode hard and put up wet." (People always gave me funny looks when I said this at college, for some reason.)
"I burnt the hair right off my tongue." (Coffee was usually the culprit.)
"Bless her pea-pickin' little heart." (I usually heard this when I was in trouble, usually for pounding nails into Mom's coffee table.)
"It's slicker 'n snot on a doorknob."
"Jeez, you woulda thought I said, 'Let's get naked and get out the Crisco.'" (She said this in church, mind you.)
"I gotta go see a man about a horse." (I didn't realize until it was too late that it meant he had to pee and that I shouldn't follow him.)
"They'll be all over you like ugly on an ape."
"Funnier 'n a rubber crutch."
Creek-pronounce it "crick."
Roof-pronounce it like it rhymes with "slough."
Hoof-same as roof.
The tiny town I grew up in has tons of people of German and Polish descent. The older folks tend to end sentences with "there," but it's pronounced "der." "The" is "da." "Thinking" is "tinking."
Example: Boat choo goin' wid jer Gramma, der?
Translation: Both you going with your Gramma, there?
I should mention that this accent is starting to die out. I can only think of one man who still sounds like this, and he's in his 80's. You can still here hints of it, but it's not as thick.
Do you have slang, accents, or idioms common to your area?