Hello,

Actually, you should have secure at least 75% marks in the 12th class board exam, or be in top 20 percentile in the 12th class exam conducted by the respective Boards. Then only you can eligible to get NIT colleges and to appear in the jee advanced exam.

The main thing is that you have to build your concentration level, then only you can stay focused on your goal. I would like to say that please limit the study time between 10 to 12 hours and please increase your concentration and speed of reading, understanding and solving the problems then you will not face any kind of difficulty.

For preparation of exam, the most important thing is your confidence after that you should know the whole syllabus and make your plan properly for learning new chapters, solving the numericals and revision. All three things should be the part of your preparation strategy in daily routine.

Your basics in Physics, Chemistry & Mathematics should be very clear upto 12th std. You should read the NCERT books for basics. Then HC Verma for Physics, RD Sharma for Mathematics, OP Tendon for Physical & Inorganic Chemistry, and Organic Chemistry of "Arihant Publication" for detail or extra knowledge. 
You should also try to solve the previous years question papers, this helps too much and you should also give the mock test to rectify yourself and build your confidence level. In this way, you can make it possible to score good marks in JEE.

All the best

• Go through with the concepts and Jee Main syllabus of Class 11 and 12th throughouly.
• Try to cover all the important topics from Class 11 of each of the domain of PCM.
• After the completion of each and every years topics, solve the previous problem of that respective topic.
• Try to complete your syllabus of Clas 11 and 12th fastly.
• After the completion of your syllabus try to solve previous 10 years JEE mains papers which will help you a lot to understand the whole scenario of IIT-JEE.
• At last , don't divert your mind from the preparation and believe on your's study rather than luck.