Don't think after some time we will do any thing we want do now

The only thing that will give you good marks is revision. Once you complete your syllabus you start revising it as many times as possible. Try solving question papers of previous years, this would help a lot. Make a habit of learning by writing because it is one of the best way to remember something for a long period of time. So all you have to do is read something try to memorize it by writing it and then revise it!