I find one of the best ways to get a great idea of a character's personality is to write dialogue, even if you don't use it. Going through it your head as if you are the character is very effective. I'm not sure how it works outside of my imagination though, so plox to be critiqueing. This scene includes Ramone, his ex-step sister, Nancy, and his mother, Bella. (whos name may yet be revised.) Nancy has just told Bella about Ramone's suspension from school.
Bella: (disbelief) Suspended? Ramone, what on Earth were you--
Ramone: (interrupting) You have no idea how much of a tool that principal is, mom. He cowtows to the will of the affluent and the powerful.
Bella: (attempting to interrupt) Ramone.
Ramone: (gesturing) HOW can a man be a respected leader when he so blatantly refuses to listen to his people? He's a joke!
Ramone: He SAID I had TEMPER ISSUES.
Bella: For Christ's sake.
Nancy: (aside, intending not to be heard) You do.
Ramone: (very suddenly, angrily) NO I DON'T.
Bella: RAMONE, this is serious, a suspension? What were you thinking, this is going to go on your permanant record.
Ramone: (frustrated) Who cares?
Bella: No, no, no, don't even THINK that, mister. Don't you DARE pretend this will just wash with me. (sighs) We'll deal with this somehow. (returns to reading suspension note in dismay)
Ramone: (to Nancy, with malice) YOU did this to me, I could've had a nice relaxing week off from school, you tart.
Nancy: Well someone has to look after your mother, Lord knows you won't do it. I happen to have a fondness for her.
Ramone: Yeah, REAL fondness you have, packing up and leaving with that SHITFACED BASTARD, taking EVERYTHING WE GOT.
Nancy: (turning red) I don't agree with any decision my dad made.
Ramone: (to Bella) This is your golden girl, huh mom? There's been MUTINY aboard this ship, (with extreme dramatic sarcasm) you must have MISSED it, Cap'n! A foul rattin' bitch like her.
Bella: Watch that damn mouth, Ramone Antonio.