People who are 30+, what career moves do you regret in your 20s and/or what choices are you happy you made?

Best decision I made was taking an internship. I wasn't really looking for one, but through some connections, one basically fell in my lap. It was in old tech I messed with in high school, so I was reluctant, but getting real world programming experience was fantastic. The team was great and I helped solve some interesting problems on a small project of theirs. They kept me on as long as they could (>1 year). I think people can be way to idealistic, especially when starting out. Go get a year or two somewhere, anywhere. You'll have a ton more marketability and control over where you end up with experience and professional references.

Biggest career regret was waiting around afterwards for a time to try to get hired on at that same place. Not a ton of programming jobs locally and I wanted to continue my work there, but the company went through semi-frequent growth/shrink phases, and my team wasn't able to get me hired in, though they did try for a while. There were plenty of other good things happening in my life during the down-time after this job and before the next, so it's not really something I regret, but I definitely won't wait on a company like that again.