Based on what has helped our local gaming club grow here (on the Texas A&M campus) one thing most people don't think of doing I recommend:

Social events...

Events where gaming isn't part of the process, or is a sideline. For example, given a lot of people won't be around for spring break this weekend instead of our normal meeting we're having: Smash Brothers Party/Battle of the Baked Goods and next week will be a movie night. We've head cook-outs and tried (but failed) to do a water balloon fight when the freshmen first got here.

I think it has helped retention...our membership has over doubled and most are freshmen or new grad students.

Why do they help? I think they create non-gaming bonds, get people talking about the rest of their life, keep people from dividing into their groups and never talking, and (although I hate to have to add this) keep away the rare individual whose habits and such contribute to the nasty stereotypes of gamers that scare other new members off.