Man, one thing that too many H/S kids underestimate is hygiene and clothing. Also, give working out a try! (After you turn 16. If you do it before, it can stunt your growth.)
Hygiene Breakdown:
Keep your finger nails manicured, (Don't pay to have them shits done, but keep them trimmed, invest in a emery board, and
maybe a clear coat. Girls notice, trust me.) Keep your teeth brushed damnit (Also, girls ask for gum all the time. Keep some of that on you too!

)! And stay showered and smelling good! Wash your face! Invest in some Axe (Its cheap and I get more compliments on my Axe than on my expensive colognes.), and antiperspirant (girls don't like sweaty pits man....for real...).
Clothes Breakdown:
Unfortunately, H/S is a very trendy place, complete with people who don't really know what kind of style they want to fall into. Therefore, brands like Abercrombie and Fitch, aeropostale, and whatever the hell else kids are wearing these days, are seen as cool and fashionable. I say, fuck this. Try to look nice, but not toolishly like one of the heard. If you wear a polo...dont wear Sperry's man! Wear some Nike 6.0's or something. Ask your mom to give you a lesson on matching your clothes too. <<< That becomes more important as you get older! Make sure your clothes are clean too!!! Ask chicks at clothing stores to help you out, you'll come out looking good, and you'll get to mack on slightly older chicks!
Working Out:
Okay, so what you guys might not know yet is that after graduating, a lot the fat kids will get skinny and a lot of the jocks will join fraternities and drink themselves into obesity. Stay on top kids, don't let your bodies go! Stay in shape by playing sports. If sports aren't your thing, then try forcing yourself to take a walk/run/skateboard/bike etc. Try lifting some free weights. If your not in shape, get into shape. Don't believe what the TV tells you, "It's not your fault!" No...it is your fault (It may be the way your parents eat and the way they taught you to eat, but you make the final decision to put it in your body!).
One of the reasons I put emphasis on these points, is that if you cover them, there is a greater air of confidence and chicks dig the way you look/smell. The rest of it, you can gather from the books and posts I'm sure you've already read/will read.
Wow...the things I wish I had been told in H/S! Good luck!