• Solve all last year question papers.
• Make your own notes in form of small points and formulas
• Revise your notes daily
• Always have good conceptual knowledge in mostly asked topics
• Refer standard books and NCERT books.

) Try to devote about 5 hours on working days, and about 12 hours on non-working days.
2)  The schedule that works best for me is to take afternoon nap for about 2  hours. If you are studying since morning (in school or at home), you  tend to be less efficient in the afternoon. Better take a nap, and study  late in the night.
3) When you have break from school (autumn break,  break before and after preboards), try sleeping fewer hours - for me 6  hours worked fine. My usual schedule involved getting up at 7 am,  studying till afternoon, nap from 3 pm to 5 pm, studying from evening  till 3 am, and sleeping from 3 am to 7 am.
Don't sleep until late in the morning. Sleep by 2-3 am in the night, so that you don't feel tired the next day.
Change this habit of afternoon nap close to the exam (about one week).
4)  Try to utilise school time: CBSE demands 75% attendance. There is no  need to have more attendance than that unless you really learn a lot in  the classes. You can skip going to school when there are fewer lectures.  Utilise free time in school for studying. Don't spend undue time on  completing practical files - just complete them in the minimal possible  time.
5) Go out for walking / jogging / cycling for 20-30 minutes in the evening, to refresh yourself.

Some general tips:
1) Avoid studying on the bed: You tend to be more lethargic on the bed.
2) Keep your phone (if you have one) few metres from you when studying.