Check with the college you intend to apply to. Not all AP classes will do you any good; for example, the college I went to would NOT accept AP Physics credit, even if you got a 5 on the test (no question, they won't take it).
Otherwise... I don't know, do homework faster. I don't think homework ever took me more than 1 hour a night in high school, and I had a full schedule of AP classes (I never did homework while in school either). This is easier than it sounds: get in the habit of outlining your work, if necessary list out the information provided and the goal of the question. This can be helpful as sometimes the goal is not clear, or you become distracted on the way there (for example: one problem in nuclear physics required me to look up properties of an isotope online. Five hours later, I have in-depth knowledge of the Chernobyl disaster... and I'm not done with the problem).
Oh yeah, and if you have trouble with AP classes, get ready for college. Unless you go Liberal Arts or something else piss-easy that is a total waste of those AP classes, you'll need quick study habits anyway. Learn to outline what you read (in just your head, if necessary) and outline your homework problems. Either that, or get set to take 6 credits a semester for 7 years while working to pay the bills.