1) We should not by heart the theory , try to understand the concept practically. It will be easy to memorize and will help in gaining knowledge.
2) Try to learn with writing down the important points for difficult concept.
3) Make sure you have revised the lessons, it makes you feel confidence while attempting questions.
4) Try to learn from examples it will lay a good foundation for study.
5) Give more time to difficult subject and make sure you learn both difficult and easy subject for few hours per day, it will help you not to loose interest.