A successful open-source community documentation initiative has:

• Comprehensive documentation provided on a central, official website.
• Inline comments and user feedback.
• The most common paths on the website are the most visible, intuitive paths.
• Fluent navigation and document hierarchies. (The URL matches the Breadcrumbs matches the content. If users get lost, users give up).
• Accurate and relevant official information, well vetted information.

via In Relation To…  Improving Community – The power of good, centralized documentation..→