Read NCERT textbooks of 11th and 12th standard of Physics, Chemistry and Biology. 

After you finish each chapter solve Multiple Choice Questions of that particular chapter. 

Read everyday. Solve Questions everyday.

Don't waste time on unnecessary things.

There are many reference books available for NEET Examination. Which ever you choose to refer, refer it so well that you know concepts behind it. 

Solve previous year question papers and give mock tests to avoid silly mistakes in the exam. 

Set a timer so that you know how much time it takes to solve questions of each subject. You don't want to leave questions in the exam because time was not sufficient so practice everyday. 

Reference books like HC Verma Volume 1 and 2 for Physics, Problems in General Physics by IE Irodov, Modern Approach to Chemical Calculations by RC Mukherjee, Concise Inorganic Chemistry by JD Lee, Objective Biology by Dinesh, Pradeep Guide on Biology and there are some more. 

Refer any of these but do them well. 

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