Heyy aspirant

I hope you are talking about NIT .

Since you are a 12th student you must be clear and thorough with your 12th syllabus . Along with that you must be in touch with your 11th syllabus . Now you have very less time for preparation you cannot focus on each and every thing , thus you should list all the important topics from each subject (11th and12th ) and clear those subjects such that you can solve any question given to you . Your aim should be to solve maximum correct question and avoid negative marking . For this you need practice , so practice questions on a daily basis keeping a timer of 3hrs . You must follow a 45 minute cycle that means In a duration of 3 hrs you must give 45 min to each subject and try to attempt 30 questions.  In the left 45 min you should cross check your answers and try to solve those questions which you skipped or you weren't able to solve . This is the best strategy which if you follow I ensure you can crack JEE mains easily and your path to NIT or your dream college will be open .

Best of luck for your future .

Hope this helps .