Ensure you give the required amount of time to each subject based on your proficiency and the vastness of the syllabus.
Ensure you are well versed with each concept and topic in your textbook. Do not ignore diagrams, tables or graphs as questions can be asked.
It is strictly recommended to take a short break of 10 minutes every 2 hours even if you study 18 hours a day!
No one likes studying maths for 6 straight hours. Give yourself a mix of subjects each day so that you decrease your chances of losing interest really quickly.
Try to solve at least 5 past year's question papers to get an idea of the exam pattern and popular questions.
The moment you face trouble trying to explain a certain concept in common man's terms, you will understand that you probably need another revision.
The night before the exam is very much crucial for your exam and your exam's performance pretty much depends upon that.