You should write the text for your FAQ page and other static pages you plan to have (an "about" page perhaps). Your SE site comes with a default FAQ page, but you'll probably want to change much of it. The default editing-help page is fine as is.
Here are some static pages you might want (this is Community Wiki, so feel free to add to the list):
- Editing help (just the default)
- FAQ
- Known Issues (list of bugs users should know about). You don't really need to write this in advance.
- Attribution page. In my case, I'm using the cc-wiki license, and this page is to explain how to cite site content. I guess this would be a licensing page in general.
- News. If you don't have a separate blog for the site, you can make a news page.
- Beta. A page explaining that the site (and the underlying software) is in beta, so users should be forgiving and report bugs (if they aren't already on the known issues page). I also have a system message screaming to people that the site is beta and linking to this static page.