Do's
1) Do set a time for studying. It doesn't mean you should go home, settle and start by-hearting the things what teacher taught you the whole day. It does mean "STUDY" when your teacher teaches you. At home, you can just go through once which would be more than enough.
2) Do get clarified your doubts right away with your teacher. It doesn't mean that you are so weak. It does mean, you are eager to understand things better.
3) Do some physical activities like playing outdoor games for an hour a day. So, that it boosts up energy and keeps your body and mind refreshed.
4) Do concentrate on things you like to do the most. That increases your memory power.
5) Do try to achieve good marks. It doesn't mean that you should always get "top ranks". It does mean, your knowledge matters than your marks.
Dont's
1) Don't compare your marks/rank with your class mates.
2) Don't just by-heart the things. Better try understanding it by asking more questions/doubts to your teacher.
3) Don't get upset for getting low marks. It will build negative thoughts. So strictly avoid it. Rather, try fixing a mind set that "I'm not going to let it down this time. I'll do better next time". Preparing yourself for that matters a lot.
4) Don't lose hope on subjects that you are feeling so hard to learn. Spend time on that subject. Ask doubts to your friends who are strong in that subject. It will help you a lot in learning.