So far I've taken a few notes on each of the main characters, avoiding physical description, concentrating on what each character wants.
I don't have to worry much about a storyline outline because this novel will be based on a completed short story. Storyline done.
Right now I'm considering where to begin the story.
If you don't know about Orson Scott Card's MICE quotient (I've seen basically the same thing with a different name elsewhere, but Card's is easiest to get a mental handle on) check it out in his books How to Write Science Fiction and Fantasy, or Characters and Viewpoint.
My story is an event story, which means my story should start when the action starts--when something happens that begins the chain of events that will lead to the solution to the problem. But this story has many good places from which to begin, many potential starting places. So, I think I'll end up writing 4 or 5 first chapters and see which one feels right.