You've done the hard yards, that new feature or bug fix now works just as you'd like - now all that is left is to submit your Pull Request, get it ...
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Great list! I think breaking things into other PR's and/or Issues is super important to a good PR process
I especially agree with #1, and wanted to add one more reason to keep each PR as small as possible. And that is to aid the people reviewing your code! Not only is there less likely hood of bugs, but it also just makes it easier to review!
You'll have been working on this change for awhile, and it feels familiar to you since you wrote it. But, unfortunately, your reviewers are coming in a bit blind and won't be able to easily understand as big of a solution right away. So the smaller and more focused you can keep your PRs the easier the process can and will be for everyone!