Jee is considered one of the toughest exams of India.
First if all Just start with the syllabus
1. Analyse the syllabus wholly.
2. Highlight the topics which you haven't read yet, and start with them.
3. Make a routine and divide the timing for the three subjects.
4. If 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.
and then further refer the standard books.
5. After completion of every chapter, you practice the DDP and study material of any good coaching or else, practice previous years questions is also important.
For physucs, i would recommend you to study and practice D.C Pandey.
For chemistry, ncert +RC Mukherje(physical) , I think that would be enough .
After, completing your syllabus, probably in the month of December, start giving test series of a good institute or may be online as there are so many online source.
Follow the link for tips and guide regarding JEE preparation :
IIT/JEE 2020 Online Preparation
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