I started out as a mod because I was really involved in the standup forum. I noticed that no one was actively modding it, and that people were flaming the shit out of each other in there and ruining some threads, that there were redundant threads, and that some bad/dangerous advice was being given out. So I PM'd an adminstrator about it and offered to help out. Not necessarily as a moderator but just in general. They turned around and said how'd you like to moderate? I'd been trying to make helpful posts, I had several years of muay thai experience, and had an education and relevant work experience, too. So I said, sure. I think I only had a couple hundred posts under my belt at the time.
Now I cruise and moderate all the forums. I don't really go into the standup forum much anymore. Because it got too repetitive for me and there are other excellent active mods in there now.
Don't know if that helps answer your question but that's how it went down for me.