mommyfollows at 2012-07-31 15:50:39:
I like to start off thinking about their demons and how those affect and are affected by the story, since it's all interconnected. This happens for me during the story construction. I can't separate it all.
I also consider how they treat the people around them, and how they perceive/are perceived by the people around them, and why. What kind of atmosphere a character's very presence evokes, how a character presents himself.
The demons and any pertinent related elements are very specific, but the rest of it is just a general impression of a character to me, very much like the general impression I have of any given real-life person. Helpful as a way of judging whether an action or bit of dialogue rings true to my notions of them. I don't write a lot of that down. It just sits up there in the attic.