Practice most from NCERt books and reference books like OPTandon for Chemistry, rd sharma for Mathematics and IE Irodov for Physics . Revise all fundamental and join top coaching institutions like Allen, RaoIIT, Akash, PACE, etc. 

Solve out all doubts and appear for more than 30 mocks  

Analyse weak areas and solve similar questions frequently to eliminate it. 

• First just go through with the JEE mains and Advance syllabus thoroughly.
• Then after that prepare your time table in that according to your convenience prepare your time table in which all the subject has to be mentioned with the proper timings.
• Try to do the mock test of every topics after the completion of that respective topic
• In your time table make some 10 - 15 min break in between the study hours.
• Always try to play some sports in evening such that you will be mentally as well physically fit.
• Lastly , believe on your preparation rather than your luck.
• Try to do previous 10 years IIT-JEE papers which will help you a lot to understand the whole scenario of IIT-JEE.