I haven't had very many characters leap out at me, but once I've created them, they usually take off and do whatever they want to do. In my 2006 NaNo novel, the main character decided that he absolutely
could notbe 13, and had to be 16, and I said, okay. He also decided that he was going on a quest to find his dragon, which I did not expect
at all. And the entire story changed when my writers meetup group started talking about cultural mores and how some cultures didn't think it was a bad thing to leave unwanted babies to die of exposure. Guess what happened to my kid?
I will say one thing, though...nearly all of my characters demand that they get to learn magic, at least in some form. How they go about it is different in each story, for which I'm thankful.
Sometimes I do find it helpful to write down a few facets of the character, just for reference. I try to find a picture that resembles my mental image (or forms it), or failing that, I draw him or her. Sometimes that's better, or at least it was
this year...
~Cal