Jot down notes. Notes will help solidify material in your head and will also serve as important study tools before a test. Be sure to write down everything important that the teacher goes over. If it helps, ask for a print out of the powerpoint beforehand so you can focus on taking notes on what the teacher is saying, not just copying down what is on the board. If the teachers writes something on the board and they underline it chances are it's important or it will be on future tests.
When you pick a question to answer, make sure you know the answer and the question is not too easy. Don't worry about asking too many questions; it's the teachers job to help you.
Review at home. Do this in a quiet place with no distractions. If the computer is in your room take it out or go to another room! Don't study with the radio on! It might help you write more but on the day of the exam the only thing you'll remember will be the lyrics.
Rewrite notes. Yes this may sound boring and time consuming but it's been proven to help you remember more of what you wrote down. It also help you to figure out problems you might have had in the class.
Put effort into your homework. Though it seems like a torture device, homework is a way of controlling and making progress outside of the classroom. This isn't very comforting the night you have two essays and algebra to do, though, so remember to do the actual homework and keep up with the workload. If you're having serious difficulties, talk to your teachers and parents to come up with a schedule for your homework.
Take a practice test before the exam to further your understanding of what you need to study. Be careful, though, taking dozens of practice tests is a much less effective way to study than combining one or two with other forms of study.
Take breaks now and then. Instead of multitasking, set aside a certain amount of time to do just homework. When that set amount of time is over, take a 20-30 minute break to keep your mind from getting tired. When that time is up, go back to doing 100% homework.
Study with friends. Reviewing with your friends during free time can help keep you and them focused and may be handy. But everyone's different: if by studying with your friends you sit with an open textbook and gossip, it's better to work alone. Know yourself and your habits.
Ask for help. Review guidebooks may help you in classes which you are struggling. Alternatively, you could go to the teacher for extra help, have a friend coach you, or ask your parents to hire a tutor.
Learn from your mistakes. Pay attention in class when something is being corrected. Mark your work clearly and carefully so that it is useful in preventing other errors in the future.
Study during the holidays and vacation from school. If after the holidays you have a test and have not reviewed over the holiday period, your mind will have switched off, and you will have forgotten a lot of things that you have learned before the holidays. Therefore you are likely to fail the test or do badly in it.
Get a book at your grade level for any new class subject you will be taking next term such as Chemistry, and read or scan it closely. Look at all the illustrations, charts, definitions, and learn things like the chemical symbols (C is carbon, H is Hydrogen, Zn is zinc, Au is gold, Ag is silver, etc.); read chapter summaries.
Treat the holidays like any weekends: Yes, you can relax and have fun, but study at least 3 times a week so you don't forget everything you have learned.
Ask your parents or friends to sit with you and review over what you have difficulty with, or that you need to memorize and recite.
Relax. Don't freak out over tests. Start studying more than one day before the exam so that you have plenty of time to ask questions when you don't understand.
Sleep well every night. Sleep will improve your memory and concentration skills, which in turn will lead to you doing better in school.
Be persistent! Don't only start well and let it fall apart; keep you study plans active and working for your success. Reward yourself when you do well.
Join extracurricular activities. This will allow you to make more friends, do something fun, and have something to add on a college or even job resume to show people that you are a well rounded-individual.
Find something that you enjoy doing to balance out the school work.