Board textbooks are to be referred along with it also refer NCERT textbooks of 11th and 12th standard of Physics, Chemistry and Mathematics. 

Solve multiple choice questions everyday. It would be best if you start preparing from now itself. 

Makes notes of every chapter every concept and also formulas. Notes would help you to revise before exam. There are many different types of reactions in Chemistry which can be remembered by writing them everyday. 

After finishing a chapter solve questions immediately and if any doubt arises then clear them at that time itself. 

There are many good reference books available for JEE Mains and Advance like Concepts of Physics by HC Verma by Volume 1 and Volume 2, Problems in General Physics by IE Irodov, Chemical Calculations by RC Mukherjee , and there are some more. 

If you still have any queries feel free to ask in the comment section down below.