Update release instructions

CONTRIBUTING.md

@@ -542,7 +542,11 @@ like the following is a useful way to check what has landed:
  $ git log --oneline v0.62.0..HEAD
  ```
 
-Also worth checking the [next-release tag](https://github.com/rust-lang/rust-bindgen/pulls?q=is%3Apr+label%3Anext-release).
+Also worth checking the [next-release
+tag](https://github.com/rust-lang/rust-bindgen/pulls?q=is%3Apr+label%3Anext-release).
+It is very important that you do not rename the `Unreleased` section of the
+changelog as this will be done automatically using `cargo release` on a further
+step.
 
 ### Merge to `main`
 
@@ -601,4 +605,20 @@ cargo dist init # from "cargo install cargo-dist"
 cargo dist generate-ci # to update .github/workflows/release.yml
 ```
 
+### What to do if a Github release fails
+
+If the release process failed after you run `cargo release` you can manually
+delete the tag and release from Github. Also remember to delete the tag locally
+by running `git tag -d`. Once all the extra changes are in the `main` branch
+you can trigger a release by creating a new tag using `git tag` and push it
+using `git push --tag`.
+
+### Create a new crates.io release
+
+Go to [the Publish
+workflow](https://github.com/rust-lang/rust-bindgen/actions/workflows/publish.yml)
+and run a new workflow using the "Run Workflow" button.
+
+Remember that crates.io releases cannot be deleted!
+
 [prettyplease]: https://github.com/dtolnay/prettyplease