[DoronS]

As people have mentioned, robot demos definitely get a lot of people hooked. However, don't just show off the robots, but let prospective newbies drive them!
You do have to be careful about mentioning college to people. The people who sign up for the ability to add robotics to their transcript generally quit the team pretty quickly once they figure out how it actually works. We'll mention it it on one of the posters that we put up around our school before our interest meeting, but at the actual meeting we're very careful to emphasize that while FIRST involvement is a powerful tool, you will only get out of FIRST what you put into it...