I became a moderator by responding to Zuperman's request for interested parties to apply. I did so via email. I also posted my interest on the forum and asked for support from those members who thought i would do a good job.
As for becoming one now, I would suggest contacting Zuperman. He makes those decisions. You may want to discuss the matter first with some of the forum leaders (squad leaders and the like) to get their support and advise.