Regarding routine and schedule:
1) 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.
Approach:
I would suggest Four Phase Approach, that was recommended by Manmohan Gupta (maths teacher at VMC):
Phase 1 – Learning Phase
In this phase, you should
(a) Attempt the problem. Don’t jump to the solution immediately. Try at least 5-20 minutes. 5 minutes, if you don’t understand question properly and 20 minutes if you are getting ideas or almost solve it. So average time spent on each question should be around 10-15 minutes. If you have solutions, refer them otherwise mark them and refer solutions later.
(b) Mark levels. After you have gone through the solutions, you need to decide the level of the question and mark it with each question. There can be 4 levels.
Easy : Problem is easy if you are able to solve (without even looking at the solution) it in less than 5 minutes.Average : Problem is average if you are able to solve it by just glancing the solution. You look at the solution for less than 1 minute and get the idea. Or you could do it yourself by trying hard and spend more time to solve it.Difficult : Problem is difficult if you are not able to do it yourself (after spending lot of time) and to understand the solution you have to spend more time on each step and finding little hard to understand the steps. But finally able to understand solution very well.Very-Difficult : Mark a problem a very-difficult if either you are not able to understand the question or question is clear but finding almost impossible to understand the solution or you find either question is wrong or solution is wrong. Don’t waste time on such questions. May be you can tackle them later when you get time. But at this stage they are useless and pull your confidence down.