Hello,
To score a very high percentile in JEE Main, you must study smart and practice regularly. First, complete the entire JEE Main syllabus from NCERT and other standard books. Understand concepts clearly instead of just memorizing. Then solve a lot of previous year papers and mock tests to know the exam pattern, important topics, and your weak areas.
You can refer the below link for a structured plan.
https://engineering.careers360.com/articles/how-score-100-percentile-in-jee-main
I hope this helps you.