More scribblins? Yes please!
Maybe it's obvious, since I'm an illustrator and all- but I am a very visual learner. What this means when I'm developing a story is that I often don't understand something until I draw it. For example, I didn't really know what my character's apartment building was like, until I drew it.
The very act of drawing opens up her world to me. My mind wanders as I'm doodling- who are her upstairs neighbors? Who lives next door? Where is the laundry room? Will the neighbors mind if she roller skates in the house? Maybe writers do this sort of exercise in a "writey" sort of way. Me, I can look at this doodle & remember the feelings I was having and the world I'm trying to create.
Similarly, drawing her (ex) best friend helped illuminate her character to me. I knew she was very pretty, a little bit plump and a lot bit vulnerable... but drawing her makes me feel her character more than writing those things.
(click for a larger view)
In my picture book classes at Pacific Northwest College of Art, we often talk about what comes first, the pictures or the words. From interviews I've heard, Maurice Sendak wrote his text before illustrating anything. I tend to come at it the opposite way- I think in pictures first, and add the text to support what I've drawn. Maybe it's unwise to go against the ways of The Great One, but I think every author and illustrator needs to find the system that works for them.