Concentrate!! Enjoy your studies!! Excel in exams!!
Do you remember yourself reading sentences after sentences of your books, but without actually concentrating on it? That is called a casual reading. A casual reading through the books doesn't help much. That is because, the concepts just pass by the mind, without being able to associate themselves with your understanding, or your memory. But the time that you spend in such casual reading never comes back. Moreover, it is boring. Study without concentration is an utter waste of time and energy. Avoid it.
There is no big tricks to develop concentration. If you want to improve your concentration in studies, you just need to enjoy what you read. There are books teaching you meditation, etc that claim to improve your concentration. I have tried a few of them, but personally I feel that the claims are over exaggerated by the authors. I discovered a simple technique that simply works wonder for me. I benefited immensely from the technique, and now I want you to benefit from the secret. The secret to concentration is being able to develop interest in the subject.
Simply stating, information is not at all interesting. But most curriculum books just provide information. Even intellectual concepts are presented as if they are information. That is the reason why curricular books are so often dreaded by students. But information becomes interesting when we discover the underlying concepts in them. So if you want to make your study hours interesting, try to discover the concepts yourself. Do not just believe what is said in the book. Let whatever you have to learn, be learnt not just as information, but as concepts that YOU have re-discovered.
If you have genuinely followed up to this, congratulations!!! You have noted down your success, and before the exam, when everyone else will be cramming, you are revising your success as a fun game.