Ever have a slippery character who just won't let you pin them to the page? Interview them into defnition with a rigorous Q&A session. I sometimes find it helpful to ask my characters questions and then try to formulate logical replies based on their psychology, sociology, and physiology (see my post on character PSP for a longer explanation).
Take your typical warmongering wizard:
Q. (Interviewer) So... did you always want to rule the local hamlets?
A. (WW): That was a recent development, actually. I was originally trained as a Palace Prestidigitator, but I couldn't take all the whining from the royal court: Whip me up a love potion for the next masquerade, gimme a dragon-slayer's sword, find me the perfect princess, glass slippers included, blah blah blah. That's when it hit me: No offence, but why serve mortals when they were so much better suited to serving me?
Q. Excellent point. Can you elaborate?
A. I don't mean to brag, but my staff could incinerate you in 1.5 seconds flat. The average mortal could barely manage to latch their sandal in that amount of time!
Q. Fa-fascinating, truly. Favorite banquet dish?
A. Hmm... I'd have to go with roasted swan with braised shallots, though my mother's mutton pie definitely comes in a close second.
Q. Favorite pet?
A. I had a Baltic Leviathan once. Poor girl, I had to get rid of her. Sweet Fang kept eating all my siblings. Besides, I'm terribly allergic to leviathan scales. Reverses all my spells when I sneeze. Oops. Shouldn't have said that. Don't take this personally, but I'm going to have to incinerate you. Privacy is worth a troll's ransom these days, you know.
Q. But I haven't asked you about your first love yet--
A. She was a witch. Smashing good one, too, until that hideous house fell on top of her. Most unfortunate. Now, would you please stop fidgeting and hold still? This will only take 1.5 seconds . . .
I don't use half the silly stuff generated by this exercise, but the rambling Q&A jam often helps me to get a better idea about my character's motivations.