Character biography. Now that you know who's who, here's a template for figuring out how they got to the situation in your novel. When it's time to write a flashback or refer to a past event, you'll breathe easier (and save yourself some edits) knowing you can look up the dates in this simple timeline.
Snowflake method checklist. Maybe you'd rather work from the top down than from the ground up. Inspired by fractal geometry (really!), Randy Ingermanson's "snowflake method" grows an entire novel from a single sentence. Each step of the process methodically expands upon the one before, filling in detail until you have a complete draft.