You can fill out most of the Common App or whatever applications your colleges use (the easy stuff) and figure out which teachers you want to get recommendations ASAP.
Between now and taking the ACT (if you're really bogged down and your scores are OK, I wouldn't recommend taking the SAT too), concentrate on studying for that and begin writing your essays. I definitely second what Rebelution90 said. Those things killed me when I was applying. Try to get the content down in some drafts by the time teachers really start getting into schoolwork and homework. That will allow you to be able to keep up with classes while only having to do proofreading, get feedback, and make minor adjustments.
Depending on what ECs you are involved with, try to tone down your involvement (I know it's not possible all the time). But by the end of the year, you'll be so freed up, especially to study for your AP test.