Coming from Programmers where we've had entire wars over site scope and the FAQ, I think it'd be good to get this hammered out as soon as possible. So what should the FAQ contain?
Wait a few months, see what questions people ask frequently, and there's the answer to your question.
Some websites have fabricated FAQ pages. They guess at things visitors might want to know, and write questions and answers. Maybe the information is accurate and useful, but the FAQ concept is treated a writing format. The worst-offending sites don't even have a good description of what they're all about, who runs it, what they offer - it's all shoveled into the fake FAQ. "Frequently Asked Questions" ceases to mean much.
We shouldn't do that.