Start making polls about what people like, find out the exact demographics of your users, and then build email lists from there, because a targeted email list is $.
With those lists you can then in the future send out targeted emails with affilate or related offers that will convert high.
Also on top of the polls throw in some surveys, but the ones that YOU get paid on submission.
As well as throw up some zip/email submits banners as that will probably get a few signups.
And always stay active and keep your voice active on the site, make yourself the "TOM" of your site, the better interaction the users have with the site owner/admin(s) the better.