On the site, interviewinghollywood.com, there is an interview with writer/actor/director Carl Gottlieb (he wrote the screenplay of "Jaws," among others).
For his observations about the two types of writers and how they work, click here.
For his ideas about creating characters, click here. (I was particularly interested in his comments about the characters who appear in his dreams and his instant knowledge of their backstories--it ties in very well with my theory that you can tap into your right brain to discover characters rather than having to strain your left brain to create them--more about this another time!)