Point 2 is the most important.
Regarding point 1, it's discouraging if the CONTRIBUTING.md has too many/strict rules.
1) Every project seeking collaboration should have a CONTRIBUTING[.]md page with guidelines.
You wouldn't believe how many people are struggling with and are afraid of the basics:
Do I need to fork first? Should the change be a branch on my fork, or on master? How to do a proper PR? Etc
2) Maintainers should provide Good First Issues on GH , well scoped, with clear description and what's expected (DOD), and (most importantly) hints/instructions how to get started to encourage
3) These would ideally by encouraged by bounties (sats)
The absolutely most brilliant reference project on how to encourage and empower collaborators is nostr:nprofile1qqsq4qcw4c0z3jq3nlselj46qxumysl8hndd8sgy89r6nxq2c8jlspspzdmhxue69uhhqatjwpkx2urpvuhx2ue0j5k08k .
Discussion
Yeah, CONTRIBUTING should be basic instructions on forking, branch setup/naming, setting up Dev environment, making a good PR etc