As i've learned from Howardforums (and a couple of the total dick mods there) you can become a mod many different ways:
1) By sucking up like someone here ;-) in hopes of being deemed "useful" and given the power to artbitrarily kill posts at will
2) Knowing a mod supervisor or site owner
3) Owners of popular websites and tech columns can be offered the position of mod
4) After 10,000 posts, some top guy feels like if you haven't been banned yet, hey. You're mod material
5) Sometimes it's a cop thing. The douchier you are, and the more you report people for petty crap like "personal attacks", the more likely you'll be seen as teacher's pet and offered the position
I've been a mod in the past on danger forums, mda/smartphones forums at multiple sites and have been a site administrator for several years. Killing posts is fun. They can always report to the mod supervisor and get me closely looked at