Hey! I'm in the same position as you! =D
For chem, I usually don't study very much because I'm in general right now and it's a review from what I learned in high school. (not trying to sound cocky! >_<)
I just know to memorize the formulas and how to solve the problems since chem is more about mathematical problems and that's usually where the points matter on the tests. Then I look in the textbook for questions/problems and figure out how I would solve it and how to start it.
For bio, it's all about memorization. @_@ but my teacher actually told us a plan schedule for how to study.
Which is basically studying the class material of the day's lecture and the lecture before that, so when you get into lecture the next time you already know the material pretty well, and you just have to add on an so forth for the next night. So when it comes to test time, you've already gone over the material at least 5-6 times. So that eliminates last minute studying. It's worked pretty well for me so far.

at least for bio.
But yeah, tutors can help, I dunno about your school but we have free tutors at my school so that's always handy. :]
and flash cards, but those never help me, because I just end up getting tired of writing them down... >.> hahaha.
Good luck :]