Keep the following things in your mind to study well.
If you learn to remember, you will forget but if you learn to understand, you will remember.
Take small breaks between study sessions to keep you fresh. Long sessions without any break lead to loss of concentration.
Learn to enjoy: Learn to enjoy what u do, to achieve the best results. Whether it is an exam, a sports event or your career, try to find the fun part in it.
Plan your time: Always create a work plan that suits you and stick to it. Research has proved that people who plan their tasks do well then those who don't.
Clear your mind: If there is too much on your mind, your work efficiency will drop.
Sleep well(not too much nor too less).
Make deep breathing your habit to improve your concentration and other benefits, before you sleep.
Benefits of deep breathing: a) Releases tension b) Relaxes mind/body and brings clarity c) relieves emotional problems d) massages your organs e) relieves pain and there are many other benefits you can use internet for search for technique of deep breathing.
By concentrating on our breathing, deep breathing allows the rest of our body to relax itself. Deep breathing is a great way to relax the body and get everything into synchrony. Relaxation breathing is an important part of yoga and martial arts for this reason.
Lie on your back.

Slowly relax your body.

Begin to inhale slowly through your nose if possible. Fill the lower part of your chest first, then the middle and top part of your chest and lungs. Be sure to do this slowly, over 8 to 10 seconds.

Hold your breath for a second or two.

Then quietly and easily relax and let the air out.

Wait a few seconds and repeat this cycle.

If you find yourself getting dizzy, then you are overdoing it. Slow down.

You can also imagine yourself in a peaceful situation such as on a warm, gentle ocean. Imagine that you rise on the gentle swells of the water as you inhale and sink down into the waves as you exhale. This technique will help you to sleep well.
Exercise regularly, go for morning walk, participate in sports to keep your self mentally and physically fit.
Positive company: Always strive to be in the company of successful people. Their personality will
reflect a positive attitude in you to perform your tasks well.
Detailed Eye: Make a habit of developing a detailed eye for inspection in your tasks. People who
do their work half heartily cannot achieve success.
Never ever cheat in test nor in exam: If you are not prepared for the test, tell your teacher about
that and (after taking permission from your teacher) sit at the back, learn it by heart and then give a oral or written test.
Don't be a bookworm: Don't just study n study, your body and mind need some fresh air and
rest. After one hour study give break of 15 minutes and then study.
Play brain games such as chess, scrabble etc. because the more you use your brain, the better it gets. Brain games are also available on internet.
Observe carefully: Carefully observe what you see and experience.
Listen Attentively: Attentively listen to your teacher during lecture.
Ask Questions: Never hesitate to ask questions. Don't worry whether your class laughs at you because they think you are asking a stupid question because this little stupid confusion may cause you problems in learning.
Stronger base: Stronger your base because if your base is weak, you wont to able to learn further things with clarity.
Try to research and study by yourself instead of taking tuition from someone and then ask your teacher to clear your problems.
Try to help your classmates: Always help your classmates with study because that would be a revision for you and also because you may find/identify your problems relating to those topics while teaching them. Moreover it would help you in keeping a good relation with your classmates.
Always revise your classwork at home after doing your h.w or preparing for the test.
Read your chapter when you have time so that you will get revised when your teacher will give lecture about that topic. Moreover you would be confident in asking questions in class.