Get hot chicks and make them do carwashes in bikinis, then post the pictures.
Actually, on the serious side, Steve, you'll find that a lot of the people that come out to those things just want to ride without having any responsibility to a larger group. I know you need people to be a club, but be very selective in who you let in. Also, usually it's not the most talented riders that will help your club, it's the hard-core average rider who wants to put in lots of time for rides. Just get a good balance of really good guys and the guys who'll do anything for a ride.