I originally wrote more, but thought better of it. All the things I listed, I heard when I was also in HS, but they meant nothing until I actually had to deal with it. Advice is tricky business. So here's two for the immediate future.
Date girls and get use to rejection - Things don't 'just happen' for guys (assuming you are one), so get out there and make some magic happen. Keep in mind that girls (and guys) sometimes have no idea what they want, and it's not always you. I use to think this was a natural thing, but like most anything else, it just takes practice. The skills you learn here you'll find applicable to a lot of situations where you'll have to deal with others.
Date girls and get use to rejection - Things don't 'just happen' for guys (assuming you are one), so get out there and make some magic happen. Keep in mind that girls (and guys) sometimes have no idea what they want, and it's not always you. I use to think this was a natural thing, but like most anything else, it just takes practice. The skills you learn here you'll find applicable to a lot of situations where you'll have to deal with others.
Cultivate a sense of curiosity - For that, I refer to you Bill Watterson of Calvin and Hobbes http://home3.inet.tele.dk/stadil/spe_kc.htm