If you want to have a group like Nman's that is mostly funny spam, you need to develope friendships with active users who like to spam and then post 4-5 funny games that are relatively mainstream, not too radical or potentially offensive. then you have to post on othher peoples groups actively so they will reciprocate by posting on your group.
As I have told a few people, it is a little easier when you have more members even if all of them are not active because it gives your group the full parking lost effect.
Sometimes store owners will encourage people to park in their lot because a store with an empty parking lot is not as attractive as a astore with a full parking lot.