Pull requests are collaboration workflows
A pull request is a hosting-platform feature for proposing changes from one branch or repository into another. Git itself does not define pull requests; platforms build this workflow on top of Git branches and commits.
Prepare a reviewable branch
Keep commits focused, remove debug code, add tests where appropriate and write a clear description. Reviewers should be able to understand the purpose of the change and how it was verified.
Review is part of development
Use comments to discuss behavior, maintainability, security and tests. A good review is not only about finding errors; it also improves shared understanding of the codebase.