My part was to support Marj, writer of the Rotaida books, and possibly to teach children a bit about how an illustrator approaches showing who a character is. We each spent two days preparing, in a very logical way, with illustrations and sample sentences. At the last minute, I created a penciled figure children could draw clothing on to illustrate a character of their own, and tossed in my runestone stamps, for some good old hands on activities.
Of course, we didn't exactly get to do our mini-class. Neither of us works quite as logically as we were trying to teach, and the children went straight to the hands on activities. THEY didn't want something that smacked of academics once school was out! As I joined them in creating a character, I tossed aside the step by step instruction handout I had created and let my character just become who it would as I drew, just as the children were doing.
I think there is a place for both ways of working, depending on where you are in the project: from the inside (letting the character develop as you write or draw) or from the outside (determining the person's character traits and then deciding how to write about or draw the person).