Our team recurits by letting people know where out there! At school open houses and activities, we make sure to let people know to come check out the robotics team, and we make announcements for our school before build season comes up, to get interested people (who can so no to building a robot!?
). Last year we also went to one of the Grand Blanc Middle School's and demo'd our robot to them. Spreading the word by mouth, or just wearing team apparel, has helped also. I know we pull from various places, between the few of us in band that get our friends, getting people from advanced math and science classes, and the teacher who teaches the engineering classes at our school (who doubles as a mentor) encourages people to join the team/go to competitions.
This year I'm gonna try to get a short, maybe one minute, video encouraging people to join on the announcements. Show them what we do, what we learn, how much fun it is, ect.
And one of the biggest things I've noticed, is kids that really want to join, will make it there. I was very proactive in high school about trying to join our robotics team, and other students that are will find there way there.