Though not technically game writing, I’ve put together several cheat sheets and quick references for use when teaching and playing games. These references separate the most commonly-used rules from the details and distill them into skimmable lists.
For gameplay references, my goal is to keep play flowing quickly, and avoid flipping through the rulebook unless it’s to look up very specific rule details.
For TTRPG character creation references, my goal is to abstract away the mechanical details for newer players so they can focus on what type of play experience they want.