First you have complete your syllabus atleast twice once the concepts are on your tips then uh can last year questions papers which are very important atleast last 3 years paper the more you practice the more chance will be there to clear it .
You can use the link below to see the important topics for JEE Mains 2019.
You can use the link below to see the sample papers for JEE mains.
Best of luck!
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