So for major exams, almost anybody who gives half a crap is going to revise in some way.
However with some assessments, I don't usually revise and I do well. I'm not trying to sound obnoxious in anyway but I've had this conversation with my friends as well. It's not about being clever or abnormally intelligent in any way. It's just that people doze off and joke around in class, then study their asses off the night before the exam and get crappy grades. As someone mentioned before, make the best of your time in class. It's not about understanding the concept on the whole, it's about exploring its nuances. I find that if you're personally invested in learning about something, you do better. It's not a natural talent or anything, it's just that you'll think about it. For example if you're learning about Newton's equation s=ut+0.5at^2, if you care about it, you'll think what that implies. What happens if there's no initial velocity? Is this true about everything in motion? What could the graph of this look like?
of course that's just an example. But to sum up, he attentive in class, ask enough so that you feel ready to teach it to someone, and try to create the interest for yourself. It really helps