Take the time to read all of this. It will actually help a lot. I worked really hard on it because I have been in the same spot as you numerous times.
Step 1. Relax. Take deep breaths. It won't be the end of your life. Panicking only will decrease efficiency.
Step 2. Think about your grades. Which tests do you need the best grades for? So lets say you have a B+ and you really want that A- for literature. You have an A in math and an A- in biology. You want an A in biology as well. Since you're in high school, your GPA is important. If you want that A in biology, than prioritize it, but if I were you, I would go for getting that A- in literature. That doesn't mean just completely ignore math! I would study, prioritizing literature, biology, and then math. Of course, if getting that A- in literature is a harder task than said, and biology might be easier, it might be more wise to prioritize biology, but thats your concern. I would ask the teacher about your grades if necessary.
Step 3. Think about your confidence. If you're a whiz at math, chances are you won't need as much review for it as you will need for say, literature. If you're confident in all of the subjects (which I don't think you are), review won't hurt, right?
Step 4. Partition your time. You should review every day until the test. Take, lets say, two or three hours every day (for a maximum grade, I would say around 1.5 to 2, but if you don't have enough time, 1 to 1.5 hours is fine). If you have 2 hours, than based on your priority list, take about 50 minutes for the first subject, 40 minutes for the second subject, and 30 minutes for the third subject. You can move these numbers around, increase/decrease, based on how much studying you need.
Step 5. Stick strictly to this schedule until the test. If you think you have done enough review before the test, you can be less rigid about the schedule, but...
Step 6. Review, review, review! I recommend taking some extra time to review everything. Even if you think you know everything, do it again.
Step 7. Review a lot, but make sure to get plenty of sleep. It will not serve you well to be tired during the school day. Also, eat a good breakfast. Don't try skipping out.
Step 8. See if you can review during the school day (not during class time, but if you have any study halls, review the information again. It won't hurt!)
General tips:
1) Visit your teacher. Get any extra help that you want.
2) If you took notes, use them. In the future, make your notes neat, organized, and informative. Don't hesitate to go the extra step and write down stuff that the teacher told that you might not need for the test. In the case of math or science, try to see if you can learn more about the topic for maximum efficiency and understanding.
3) Use YOUR TEXTBOOK! I can't believe how many times I was saved in middle school and this year in high school by just simply reading through the textbook. Review at home using your textbook.
4) If you want to, I would recommend taking notes from your textbook as well. Taking notes on the important stuff can really help when you're reviewing, and it might be tedious, but it DEFINITELY helps.
5) Can you reschedule for later? Extra time never hurts :P
6) Pay attention in class. You might have an important detail that will help you incredibly on the tests.
7) Have friendly relations with the teacher. They might be more lenient on your mistakes.
Just don't panic, school is tough but it's not impossible :P
