There are a few very easy ways to spot a tweeker.
1. Very skinny, with especially gaunt faces
2. Complete disregard for appearance. They will have dirty clothes, be unshaven, messy hair, no makeup.
3. Appear to be much older than they actually are.
4. Brown teeth, often with many missing.
5. They have red sores all over themselves, this is from picking at their skin while high.
6. They are generally very paranoid and confused.
You can see them anywhere, in a small town it's not uncommon to see a dozen in the course of a day. Generally avoid them and don't give them the impression that you have anything of value. If you see them in a retail store, they are almost 100% guaranteed to steal something.
It's a sad transition, and almost always their journey ends in prison or death.
"Palmdale is all about the tweekers. The Sherriffs do it too."
"I heard his mom tweeks with him every time her check comes."
"Dude, stop tweeking out on it for a while, They get the point, damn!"
"Up the ass, bitch, or you don't get yo' crank!"