Heh - don't regret the partying yet. I got plenty of partying done in college and still landed a great job, so you should wait until you're out of college before you start regretting your actions there ;)
As for me, I wouldn't have picked on one of my friends in elementary school and middle school. He was socially awkward and an easy target and the only reason I can think that I made fun of him was because of how much I was picked on myself. He was a really great guy though (smart, nice ... just a little awkward) ... I just wish I could take all of the teasing back.