Hello,

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.

In this way, you can score good marks in JEE Main as well as JEE Advanced.

For more preparation tips, importants topics & books, you can go through the link given below

https://engineering.careers360.com/articles/jee-main-2019

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All the best for your examination.

Top books include NCERt books which are must alongside reference books like HC Verma for Physiscs and Ie Irodov  

For Chemistry we recommend OP tandon and For Mathematics go for RD sharma for detailed coverage and lucid information. 

List of all topic wise bestbooks below. 

https://engineering.careers360.com/articles/best-books-for-jee-main-2019