Story beats template. Adapted from the world of screenwriting, this popular method replaces the concept of acts with a set of milestones that commonly appear in many kinds of stories. Hitting these "beats" gives your story a rhythm while leaving the details open to your imagination.
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.