The biggest mistake you can make is to go to one of the "for profit" "universities". You're completely throwing your money away by doing that. You're not going to be qualified to do anything when you "graduate", and the "credits" you earn won't transfer to a real school.
The second biggest mistake you can make is to go to an expensive school on student loans to qualify you to get a job that pays complete crap. This is why at an engineering college, all other students make fun of the liberal arts students. If you want to be a social worker or teacher, don't go to a private school, go to your in-state public university that will only put you in debt for the next 10 years, not the rest of your life.
Someone mentioned HR. Graduates of Purdue's undergraduate business school who concentrate in and get a job in HR make more than any of their peers. Its a very fast track to management and a six-figure salary, and the reason it is that way is that its hard to find good people who want to do it. And I think that's the lesson. Find something that you're good at, that you like to do, that not a lot of other people like to do. Not a lot of people like HR, that's why they make money. Not a lot of people can do calculus, that's why engineers and scientists make money. Tons of people like to work with kids or fly airplanes, that's why teachers and pilots are paid like crap. Choose wisely.