Hello Goutham,

In order to get admission in NITs or a good government college, you have to score at least 200+ marks in the JEE Main examination.

In order to achieve this goal and to score a good marks in the JEE Main exam, the following tips could be helpful-
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.
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.
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 more preparation tips, importants topics & books, you can go through the link given below
Https://engineering.careers360.com/articles/jee-main-2019
In this way, you can prepare well for the JEE Main and the JEE Advanced.
Thanks for query on this platform, you may visit again for further queries.
All the best.

Hello Aspirant
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It depends on your category and it also varies from college to college. As per previous years cutoff if you want to get seat in top NIT Colleges your rank should be below 20000. For  this you should get atleast 220+ marks in Jee mains.
         But this year the cutoff marks may differs from last year because the exam held twice and the aspirants who got less score in first exam they can improve their score in second jEE mains April exam.
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If you want to know the previous year cutoff ranks of Nit Colleges once visit this below link to get clear idea about this:
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• https://www.google.com/amp/s/engineering.careers360.com/articles/jee-main-cutoff/amp

If you have any questions further let me know.
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Thank you!!!