This is pretty much already answered by everyone else, but I'll give it a go anyway.
Mods are chosen for a reason. They are good users who posts quality posts, have good judgement, report things, etc. etc. They were already helping out the forums before they were mods, as can you. Report things, for one thing. There's always some post out there that's in need of a moderation check, so look around when you're browsing a thread to see if anything is out of place, useless, and all the other things that qualify a post as worth reporting. This helps in tons of ways, I know, and I'm not even a mod.
Another good thing to do is to keep a positive attitude and be active, everywhere. All the time. Be positive and brighten up peoples' days with good content about your views on things. Come up with things worth discussion and start threads on them. Keep the forum active. A more active forum means more active users, and more active users means more friends being advised to join, and more people joining means a bigger, better forum that will very likely get more technical staff, general staff, and more features being implemented. It's just like a business. The more customers you have, the more money you get, and then you can better your business.
Being a better person and a better user motivates others to be better users as well, which leads to exponential awesomeness. Sorry for such generic advice, but this about all you can do, for now.