I daydreamed through highschool and the first year or two of university (in fourth year right now), but I've found the trick to university for me is to find those good professors who really have something to teach you, and really want you to learn and participate. This is obviously easier in social science classes where debate is naturally encouraged, as opposed to science classes, but generally speaking I've had success doing this. The sad thing is, is that there just aren't that many profs like the ones I've described, you really have to hunt around for them. One good resource for doing this, however, is
RateMyProfessors.com - Professor Reviews and Ratings By reading the comments you can get a good feel for how the prof teaches the class.
And I would like to second the fact that I really wish someone had taught me something useful in highschool, like logic or critical thinking. Although I did learn how to do taxes....but I think would have preferred just about anything besides learning how to do taxes.
Also, I know John Gatto has at least one book out if anyone is looking for some additional reading material.