Wake up early, begin with the most difficult topics, have rest. In the afternoon, study the moderate topics. At night, study the easier topics and revise whatever was done during the day.
Also - Eat well, have proper rest, give ample time to all the subjects, don't get disheartened and stay determined.
All the best ! 

Well I used to study all three subjects  on a regular basis and after studying a concept I used to implement it by solving some good and basics questions.This was very helpful as this made me in touch with my prior concepts and the other thing is that I had solved last 10 years jee papers(just like in exam hall strictly in time) which was very helpful. After each test analyze your performance and try to score  more than what you scored that day.Alternatively you can also join some good and specially relevant test series .
Always believe on yourself ,have patience,do hard work.

Hello Mainak! Prepare a time table and follow it strictly. Divide your day into different slots and study different subjects in them. Assign yourself daily tasks and finish them positively. At the end of the day you will feel good, motivated and energised too. Hope that helps.