You would have to be around here for a long time, probably at least six months. You have to prove your equanimity and calmness in the face of ad hominem attacks and other forms of abrasiveness. You’ve got to show you have the “fluther” attitude and that you’ve got the people skills to effectively implement the guidelines without pissing anyone off more than necessary. For example, you need to know how to spell well, and use good grammar, and how to avoid txt speak.
Eventually, I guess when they need more moderators, you may be invited to do so. Some people volunteer and others are asked. I suppose you have to be willing to spend a certain amount of time here. However, it isn’t enough just to be around for a long time. You have to have the right temperament. It would probably be good if you have a history of supporting the guidelines, and not fighting or complaining about them.
Of course, I’m just guessing, based on my observations of who has become a moderator over the time I’ve been here.