chore: update contributing.md

CONTRIBUTING.md

@@ -38,7 +38,14 @@ If your new derivation adds packages and checks, it will be picked up automatica
 
 ## Opening the PR
 
-The PR should have a proper description, ensuring that code reviewers do not need to ask questions about the "why" of the PR. Your code will be reviewed once all CI checks pass. If you would like early feedback, mark it as a draft PR in the GitHub UI and ping us.
+The PR should have a proper description, ensuring that code reviewers do not need to ask questions about the "why" of the PR. If the PR has a related issue, be sure to mention it in the description as well with a [closing keyword](https://docs.github.com/en/issues/tracking-your-work-with-issues/using-issues/linking-a-pull-request-to-an-issue#linking-a-pull-request-to-an-issue-using-a-keyword) such as `closes #1337`. Your code will be reviewed once all CI checks pass. If you would like early feedback, mark it as a draft PR in the GitHub UI and ping us.
+
+Some things to keep in mind while working on a PR:
+
+- All commits must follow [conventional commits](https://www.conventionalcommits.org/en/v1.0.0/#summary). This is enforced by our CI.
+- Your commits must be [signed](https://docs.github.com/en/authentication/managing-commit-signature-verification/signing-commits). This is also enforced by our CI.
+  - Aside from the requirement for this repository, it is good practice to sign your commits, otherwise anyone can trivially impersonate you on github and you can get [rekt](https://github.com/KaiserKarel/rekt). 
+- If you have `nix` installed, ensure you run `nix fmt` and `nix build .#checks.your-architecture.spellcheck` before pushing. These are both checked in CI, and if they're checked locally first it will make the lifecycle of your PR much faster.
 
 ## Reviews