Anyone with 3000 reputation on Server Fault can vote to close a question. 5 such votes are required to close a question.
Anyone with a gold tag badge in one of the question's tags can cast a binding close vote for the duplicate reason. (Only one vote required to close.)
Moderators (like me, with the diamond after their names) can cast binding close votes on any questions for any reason.
That's basically it. You can and should read the help on closed-questions in particular, as well as the on-topic help page, the off-topic help page, and the help page on how to ask a good question, but that might not matter.
At the end of the day, it's based on the votes of community members, so if the community just plain doesn't like a question, it can technically be on-topic according to the rules the rules and still get closed and downvoted into oblivion. As I said in response to my election as moderator (also by popular vote), democracy doesn't work... so there's that to keep in mind too.
It might be helpful to point out which question you're talking about, so you can get advice on whether you and your friend are wasting your time on something that's fundamentally unsalvageable.