Story premise worksheet. Your premise is the foundation on which the entire novel is built. With this step-by-step guide, you'll think about who your protagonist is, what he or she wants, and the problems or conflicts they must overcome. The end product is a concise, two-sentence explanation of what your story is about.
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.