Make good friends. Hang around smart intelligent educated 'moral' people. Form networks - these networks matter to get jobs, etc. Remember, 90% of the good things you get in life (jobs, stock tips, hot dates) will be informally, via your network of friends/colleagues.
On my first day of high school, my dad gave me a priceless piece of advice: Don't be friends with people just because they're available and easy to be friends with. Seek out the people worth befriending, and become their friend no matter how hard it is.
I didn't really understand him at the time, but 15 years later it strikes me as one of the most valuable things anyone has ever told me.