I'm testing a new thing I've been playing with a bit. Basically, if you refer a new member to the site and they create an account, you get 1 free month of Premium for every single person you refer. Not a bad deal, really.
New users who create an account are also getting 1 month of free Premium Membership as a vehicle for me to track referrals. They must select this option during registration for you to get credit! Since it's free, though, I doubt you'll have to worry about that.
All you have to do is go to your client area copy the link, and distribute it places people may be interested in signing up here. You can directly give it to people, or you can put it in your signature on other sites and watch your free months roll up without any work.