You shpuld know entire syllabus firstky and studu weightages and focus accordingly  As given below. 

https://admissions.jnu.ac.in/prospectus/jnuee/SLL%26CS%25201.pdf&ved=2ahUKEwidg4bsifLdAhVJu48KHVtLCgMQFjACegQICBAB&usg=AOvVaw1pxRqz0-iSlJl8-tTuvNmm

Practice as many mocks as you can and analysis of weak areas is must. Revise such concepts regularly an dkeep practicing. Solve out all doubts and scrutinize exam pattern.

Keep revision notes with you as well.