Hey, how did you get into poking things til they break? I just got into a comp sci program and i'm clueless about all of this.
Seriously though, I started because I wanted to secure my server. So I looked at how other people secure better severs. Sometimes I looked so deep I found errors, normally little things like leaving a default account set up, or leaving FTP wide open.
If you're looking for some generic response like "Just go to http://hunt4.bugs", I don't think one exists.