Comment by jobvandervoort

Ours is here: about.gitlab.com/handbook - it's open source: gitlab.com/gitlab-com/www-gitlab-com/

My tips:

1. Maintain a clear single source of truth

2. Make sure everyone can contribute to it. We do this by requiring at least to edits to the handbook during onboarding

3. Embrace it as an organisation: if not everyone is committed to it, it's hard to maintain it as truth

4. Constantly iterate and improve it. Structure is highly dependent on the content.