Hi Abhishek,

MA in International Relations is a highly sought after course in JNU. You need to prepare well to be able to get through this reputed course. 

Firstly, you need to be thorough with your BA syllabus with special emphasis on Political thoughts(Indian and Western), Foreign Policies, Current International affairs, Organisations, Political Economy, Globalisation etc. The concepts should be on your fingertips to be able to tackle objective kind questions.

You can seek help from standard books like The Globalization of World Politics(Baylis, Smith);  Political Theory by OP Gauba etc or whichever authors you found comfortable.

Regularly read the international affairs section of Hindu/Indian express and also magazines like Frontline to keep yourself updated. For practice of MCQ questions, you may buy R Gupta's DU M.A. Pol Science entrance guide book. You may also go through NET-JRF books of Political Science.

All the best!