I am not a Topper, but I learned a method from my father that allowed me to pass JEE advanced and KVPY on my first attempt.
In class, act as a learner and develop concepts.
Sit in class with the mindset that you're there to learn something new. So, while the teacher/tutor/friend is teaching, could you pay attention to every word he says? And, where workable, try to tie those ideas to a real-life example and, if possible, try to create a short story in your head. And, if you have free time, attempt to come up with theories that contradict those you've heard; this will help you develop a notion of the subject.