Even though I design my lesson plans each year around the interests and gifts of each class-ful of students, my first assignment never changes: start to build a character. The students can choose how to go about it, depending on their own learning and writing styles. They might fill out a character questionnaire, or conduct an interview. They can write a journal entry in the character's voice. One student wrote and illustrated a comic strip--beautifully.
Throughout the rest of the school year, my assignments revolve around these characters. The kids are free to discard the character they started the year with if they choose to; this rarely happens, since building a character from nothing really does take a lot of time and can generate pages upon pages of material (like, say, a whole novel's worth). Each week, I read selections aloud in class, so the students become well-acquainted with their classmates' fictional people--and they often become attached.
Nothing in my previous years' classes prepared me for what happened this year, in my students' final stories. The characters of each student had grown and developed so clearly over the year, and become so familiar to everyone in the class, that those sneaky little figments of my students' imaginations actually up and jumped stories.