What should be my preparation strategy for JEE Mains exam?

You should go regular coaching institute and try to collect previous year samples of JEE Mains from internet. You can also take JEE advance. You should also try to revise the subjects from class 11th.

You need to choose a good coaching center and have confidence in yourself. In the end, your efforts will matter. You can solve previous year papers and model papers. All the best.

You can join a coaching institute and also use books like Dineesh books and many more.

It is better to join a good coaching institute as well as do 4-5 hours self-study along with your school and coaching studies. All the best.