At the moment, I have the blog set so that I have to approve the first comment by anyone wanting to comment. After you get approved once, you’re good to go.
That’s about the extent of my comments policy right now; obviously I’m going to have to come up with something a bit more detailed and helpful for would-be commenters, but for now: don’t say hateful shit. That’s my only requirement. And I get to decide what’s hateful or not.