[ShaniL]

If you have a robot that you can show off during lunch, or sometime when large groups of people could see it, that would at least let people know robotics exists. Even if you don't have a past FRC bot you could show off something you've done outside FIRST.
You could also make a robotics commercial and put it on your school's announcements, especially if you have video announcements. Also having teachers tell their students about it during class is helpful. Our comp sci/technology teacher tells all his classes about robotics meetings and that helps a lot.