Sorry, adult breezing through and happened to see AP exams lol... mind you, hs wasn't that long ago for me --- I just graduated from college last year
I went to a school with over 70 AP classes to choose from so they were a big thing for us. We all went around thinking we had to take as many as possible. To tell you the truth, these accelerated classes don't really do all that much for you. When you finally get into the college of your choice and start looking at grad schools and whatnot, you realize even the most introductory college class (say, Biology 101) gives you 10x what you would learn in an AP class. Well, obviously, it is college. So even though people go: "Oh I'm going to get AP credits and not have to take that class in college" --- if you're really serious about going to grad school, you will be taking those introductory classes again. Matter of fact, most of the prerequisites to get into med schools and such, require that you take the introductory classes at a 4 year university.
That being said, taking APs is a good idea to help you get more of an edge when you do take those classes in college. Most high school classes are a joke and don't prepare you for anything. If nothing else, studying for APs might reinforce better study habits

which are really the things you have to have when everyone else around you wants to go to parties.
Besides studying from the books, I'd recommend getting together with friends to study (if you can actually study that way, many can't). But most of all, flashcards. Just go over and over them until you repeat them in your sleep lol. All Science classes are just memorization really. Anyways, best of luck to you!

And don't worry too much about getting a 5 --- when you actually get to college, it really doesn't matter that much!