As yardgames says, we don't tend to pick moderators that often. Our next moderator will be choosen probably around the 1000 - 1,500 member mark. It depends what kind of members they turn out to be, the more active members we get the more moderation will be required.
The candiates have to be senoir members, and I don't expect anyone with under a 100 reputation power and 100 post count would be thought of unless they were exceptional. Saying that at least 3 months in the forums is the minimum time period before a consideration will be made.
When it comes to moderators we don't take self nomination, and we don't ask members, it is a decision completely decided by the administration and moderation team.
Don't expect a moderator position to become free until around December or January next year. Moderators have to be very trustworthy because they have a great deal of power to delete posts, ban members etc...
J and yardgames were chosen because of their high reputation within the community, high contributions, forum loyality and the support they gave to other members who asked for it. They do do a considerable amount of work, so its not just a fancy name title, they ammend posts, move threads, edit threads and loads more - the moderator log is quite a long one!