From my school days, I am an average students, after I follow these things, my capacity to study was enhanced very well.
1) Select a regular place and concentrate fully and study.
2) Whatever you study, give 5 to 10 minutes relaxation for every 1 hour.
3) Write a short note of whatever you study.
4) Study conceptually.
5) If you are not able to understand any particular thing, write it in a small note, and ask it to a person who can guide you, or you can search for it in net. Its the follow up you take for what you don't understand.
6) Reading 100 pages a day is not a great thing, whatever you study, study it clearly and 100% clearly.
7) If you are tired of studying, you can take a note and write whatever you have studied today. (If you are not able to write, you don't know anything).
8) When you are working out problems, you solve the problems, you try to solve the problems on your own, don't see the answer quickly.
9) 50% is what you study and another 50% is your ability to apply it in exam.
10) So using previous year question paper write a model test.
11) When you are free, you can recollect what you have studied, without opening book. If you miss any point, you can then refer book.
12) Give more importance in understanding the basis concepts in the first chapter, which will help you in studying the following chapter very easily, you can enjoy studying.
13) If you are not able to understand a particular topic, dont change the subject or become sad, find out why you don't understand it.
14) Relax your mind. Be happy. Its all I have tried. It worked for me.