First of all give you most of the attention to you class 11th study.
After that start with the syllabus
1. Analyse the syllabus wholly.
2. Highlight the topics which you haven't read yet, abd you don't have any idea of that and start with them.
3. Make a routine and divide the timing for everything equally.
4. Since you are in 11th, everything would seem to be very new to you. So start with a basic book, I would suggest for the very recommended NCERT for physics and chemistry.
For maths, practice from R.D Sharma or RS Agarwal.
5. After completion of every chapter, practice previous years questions.
For physics, i would recommend you to study and practice D.C Pandey.
For chemistry, NCERT+RC Mukherjee(physical)and this would suffice.
After, completing your syllabus start giving test series of a good institute.
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I hope this helps
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The main thing to prepare for any exam is to gain knowledge about the syllabus for that exam.
So, look for the complete syllabus of JEE and try to cover this syllabus on your own or by joining a particular Coaching Institute.
You can find the complete syllabus of JEE at its official website provided below,