Developing a Protagonist

Since I'm working up a new book, I've got to have a brand-new, completely different protagonist.

When I'm working on a protagonist, one of two things usually happens…the protagonist is just immediately known to me (this happens when I've got a composite image in my head based on several people I actually know), or else I go through and build up a protagonist based on traits I admire as a reader.

I'm definitely operating from the second method this time and building up a main character...