Starting now, how should I prepare for the BITSAT and the JEE Mains ??

CLEAR YOUR BASIC CONCEPTS :-

First finish your NCERT books as these books will create your base & you can learn all the basics. Try to finish entire 11th and 12th syllabus as soon as possible. The JEE syllabus of Class 11th and 12th contributes about 45% and 55% of the IIT-JEE question papers, respectively.

DEVELOP PROBLEM SOLVING SKILLS :-

During practice sessions, develop speed in working out the problems. The strategy of solving questions, starting from the fundamentals, will spark thinking process which are essential to enhance and master analytical skill with conceptual understanding. Aim for 100 percent hit rate. This will give you a competitive edge. Speed and accuracy will also allow you to finish the IIT-JEE papers ahead of time, leaving you time for revision.

TIME MANAGEMENT :-

IIT is not about solving all questions, but it is about solving decent number of questions in a given interval of time. If you are unable to solve a question, please don't spend an hour on that, move on to the next question and try to solve easy questions rather than focusing your time and energy on difficult questions. Take more tests. Measure how fast you are able to crack. Time management is crucial in solving IIT papers.

8. NOTES :-

Take notes on the tips while preparing for the IIT exam. It helps a lot in last minute revision. Notes are your best friend during exams. They are handy. Books have tons of information which you may not need one day before exams. At that time, notes are your best friends. Always prepare good notes in your own language.

9. PRACTICE :-

The more you practice, the better it is. With practice you are more comfortable with the questions, also you fine tune your basic concepts.

10. REVISE REGULARLY :-

There is no point of studying if you don't remember it. Without proper revision we will not be able to retain things in our mind. Revision plays a cardinal role in our preparation.