Depends on what kind of FC you're aiming to make. Go around and talk with people, make friends, etc. Maybe you can convince them to join you.

If you're going with quantity however you can pretty much go the extra mile and shout advertisements everywhere, send invites to sprouts who don't have an FC, put up a party finder, etc. There's two FCs on my server that do/have done that... they're huge, but from what I gather, there's a lot of 'cliques' that have formed within them, because there's so many people and hardly anyone know each other. And a lot of people don't like them because of the whole "sending invites to anyone without an FC" thing.