Based upon your reply in the comments, I have to preface this by saying I don’t know how difficult the IIT JEE is–I’ve only heard legendary stories.
The best I can offer at first glance is to do what you can to fully understand the math and the physics so that you can visualize the systems at work. The more thoroughly you intuit the underlying structures, the more fluent you will be when asked to apply that knowledge.
Do you have a visual picture of Newtonian mechanics? The calculus? Do you thoroughly understand the derivative and the integral? Can you rotate a curve in your head and see the volume created?
Can you picture electromagnetic forces at work? Quantum mechanics, at least at the level of electron shells? How are you with the concept of wave-particle theory?
Does the exam get into linear algebra? Vectors and matrices?
When I learned calculus, physics and chemistry, I was able to master American exams through deep internalization of the underlying math so that I could visualize what was happening. I doubt that our exams are nearly as rigorous as the IIT JEE,
I don’t know exactly how to describe how I went about it on my end, but my intuition tells me that there is no substitute for knowing everything so well that it becomes intuitive. Have you tried walking through the proofs of the concepts you are studying?