I just put an ad in the local newspaper, got a total of two calls and I knew both of the guys. We set a time and had our first meeting, and then each of us recruited one or two people. We also let friends come who just like beer but don't brew, they will bring a sixer of craft beer. Now we have about eight people brewing, and we still let nonbrewers come because that way we might have 10-12 people which is a nice number for a meeting. Our meetings are informal tastings, we all bring food and just talk about brewing and other fun stuff.
I would recommend that you set a certain day of each month (third Thursday or Saturday) so people know when it is without having to be called each time. Seems theres never a time when everyone is available and its maddening to try and find a date that suits the whole gang.