Volunteer! Do it!
Having been an Ambassador at CMP back when it was at the ATL dome, I can say that it was an incredible experience. I got to meet a lot of really cool people and talk to people that wanted to get involved, but maybe didn't know how. At the time, I believe I got to show the Governor of Hawaii around, so that was neat. I also had the opportunity to meet and talk with Woodie about what I was going to study in college. Talk about unbelievable advice and wisdom
Field Reset is also great. It's fun, exciting, you get to see all the matches, you get to make friends with the other volunteers, etc etc.