This may not be a good subject for me because I don't create my characters. Not even a little. They come in as fully formed people and I don't get to dictate anything to them as far as personality or character traits go. But it wasn't always this way for me. In fact, my first rejection ever mentioned my characters were two-dimensional, so how did I change this?
The first thing I did was go to the library and read every book they had about characters. The main theme--that I can remember at least--from all these books was to create character sketches. I developed an 80+ question form that I went through and filled in for each character for the next couple of books. Some of the questions came from these writing books, other questions I took from job interview books. But between the two, I managed to compile a pretty comprehensive quiz. What this really allowed me was time to talk to my characters and get to know them. I think that was more important than the actual character sketch itself.
So do I still use this exhaustive questionnaire? Not always. I did on Ravyn's Flight, which turned out to be a really good thing because I needed to refer back to it to remember eye color and height for the spin off book. But I don't fill this out for every book and I don't necessarily fill it out completely. I didn't do sketches for The Power of Two or Through a Crimson Veil, but I didn't need to. These characters talked without my having to quiz them and provided a lot of detail. In other stories, like the romantic suspense have on the back burner, I needed the sketches because the characters weren't sharing.
I think my characters drive my stories more than a lot of other writers who come at it from a character angle. But the truth is that I let them drive the story. If they don't mention something, I generally don't either since I'm usually in one of their points of view. My take on this is if it's something the h/h haven't brought up, why should I make them think about it? They know what's important to them.
MN Weather Report: 40 degrees.
