Hey subhash! 

Firstly I would like to begin by telling that studying any course or any particular subject is hard in it's own way.

The best way to remember something is to study the same thing over and over again no matter how boring it would be.

So the first thing to do is take short notes about what ever subject you are studying and study the same piece of information over and over again. 

Second thing is sit through all the lectures listen to what is being explained in the classroom. That much is enough for any student to pass his exam.

Wish you all the best.

Hi Shubhash, you may use following tips to remember whatever studied ,

Give treat to yourself for every successful revision. 

If you are studying in group then you can explain to your friend what you have studied.

While reading notes do not speak in mind , speak it loudly.

Write what you have studied. 

I hope it will help.

Thanks.