As very less amount of time is left that is hardly 3 months,you should solely concentrate on NCERT for biology at this moment.
Take out 15 to 20 days in january or February to revise and memorize NCERT thoroughly for biology. Both 11th and 12th NCERT.
Study NCERT line by line, ask yourself questions from each line and paragraph. Don't skip even a single diagram, chart, labelling, summary of even figures in numbers. Memorize every single detail of NCERT. Memorize the labellings in diagrams.
This can be done in 3 weeks or 20days maximum. Study it in such a way that you have a nice grip over the subject and you become very confident to score well in biology.
For the rest two subjects that is physics and chemistry, keep solving questions. Keep solving as many questions as you can. Don't waste your time in reading theory, just keep solving questions all the time.
You should not get bored so keep switching between subjects and topics. For eg- solve 1 topic of physics 3 hours, then switch to chem for 2 hours, then switch to physics again 3 hours different topic and then again chemistry 3 hours different topic.
Make sure you get a nice grip on important topics such as mechanics, electrodynamics, thermodynamics, equilibrium etc.
For this you need to solve a variety of questions which involve different formulas and concepts, don't stick to just one concept.
Try questions of various degree of difficulty, don't just do hard questions you'll get depressed, don't only do easy ones they won't come in exams mostly, do good questions.
Do questions from last several years papers.
If you have joined a coaching class then make sure you don't miss even a single test of the test series,even if you have not studied for the test, just go and give the test, Atleast you'll go through so many questions. Trust me it helps.
Apart from all this, keep your personal life sorted. Avoid negative people, keep yourself motivated, share problems with parents and keep working hard. Don't stop. Keep asking doubts from your teachers, you never know what may come in exam.
Keep working hard, all the best!
