I hate to sound like a broken record, but
time management is really important. (Bonus, you can "procrastinate" right now by watching it!)
Essentially, it all boils down to doing stuff. Come home, start working. I'm a really big fan of the setting false deadlines, as Dr. Pausch mentions in his final talk. You treat a project like it is due 2 days before it is due, so if some extenuating circumstance comes up, you are okay. The important thing with this strategy is to actually treat the fake deadline like the real one, so you only slip at the last minute if you have to.
IMHO, to get things done, you've got to be intrinsically motivated. How you find that intrinsic motivation is something you've got to figure out for yourself, because otherwise it won't be intrinsic, will it?
Relate things to what you've interested in, because high school is mostly general education, so your teachers won't do it for you.