Are you forgetting formulae in exam ?
- Make a sheet enlisting all important formulae.
Are you making silly mistakes in the questions you already know ??
- Make sure to learn from the silly mistake and ensure that you do not repeat it.
Are you not able to solve certain types of questions ?
- Make sure to do ample of questions of that type.
Are you not able to solve problems of a particular chapter ?
- Make sure you saturate yourself with all possible problems of that chapter from all available standard textbooks.
Are you not able to solve questions fast ?
- Make sure you do regular revision and practice questions with a clock beside you to time yourself.
I hope that will help you
The idea is to analyse every paper you solve. Analyse your mistakes. Think of questions like
- Where did I go wrong ?
- Did I make silly mistake ?
- Is there a particular chapter whose questions you weren't able to do ?
These questions will surely help you find the issue and you are sure to do better.
All the best for JEE advanced :)