What should our documentation contain?
Much of the sites documentation will be the same as on every other Stack Exchange site: “be nice,” “how to create an account,” “how to ask questions” — it’s all pretty static. Even the sections about “what kind of questions should I (not) ask here?” comes primarily from the Definition phase of Area 51.
But the questions you want to discuss in meta are those issues specific to your site that need to be mentioned in the Help Center.
Take the Super User "About" page as an example:
Super User is for computer enthusiasts and power users.
- Specific issues with computer software, hardware or networking
- Real problems or questions that you’ve encountered
Don't ask about...
- Anything not directly related to computer software or computer hardware
- Questions that are primarily opinion-based
- Questions with too many possible answers or require an extremely long answer
- Videogames, consoles, or other electronic devices, unless they connect to your computer
- Websites or web services like Google, Facebook, Twitter, and WordPress
- Shopping, buying or product recommendations
- Issues specific to corporate IT support and networks
These are then elaborated on in SU's What topics can I ask about here? page.
It took almost a year to figure out the list of “we want these sort of questions” and “we don’t want these sort of questions” on Super User. Area 51 gave you a head start but you should also be working out other FAQ-related issues specific to your topic and your community.