Hello Nikesh Kumar Pathak

You need to analyse the papers and questions. You need to check out previous year papers and understand the way the questions are asked. Or if any previous year paper questions are repeated or not and if repeated, at what interval of time. Solve as many questions as possible. Also go through the net, and learn different things related to all the branches. You will come to know, whether you have interest in that particular branch or not.

Hope it helps you.