What you need to know
A pull request is a communication tool as well as a code change. Reviewers need to know what changed, why, how to test it, and whether screenshots or data migrations affect the release.
How to apply it
Keep the scope focused, write reproduction or verification steps, include before-and-after images for visual work, and call out environment or rollout requirements. Read your own diff once before requesting review.
Common mistake to avoid
Do not write a title that says only update code. A useful summary makes the change easier to review and easier to find later.