Here's some advice I have for you young folk that I wish I had gotten ten years ago.
1. Work out/stay in shape. Going for a jog or doing sit ups is a lot easier when you are a 190lb teenager then when you are a 230lb 30 some odd year old who has broken their ankle twice and been shot in the knee by an arrow (just kidding it was a nailgun).
2. Work a job in the summer during highschool/college and put some of that money into an IRA or some other type of retirement fund. It is worth it I think and the sooner you do it the more it will be worth.
3. Ask that girl/guy out that is way out of your league. If they say yes then great! If they turn you down then you probably made their day a little better (who doesn't like getting asked out?) and at least you will never have to wonder what could have been.