A lot of times, female characters - particularly the villains - come off as very one-dimensional. They get the short shrift in that they're only given the snappy comeback, or they're relegated to a very stereotypical role. I want to know what's driving them - that's what's really interesting.
I'm a very visual thinker, so the characters are running through my head, doing what they're doing when I'm writing them. And there'll be moments where I'll just kind of throw a look off to the side as if I'm talking to one of the characters. It's always been something that I've had with me since I was a little kid.