For me, I just tried hard to relate all the material. When studying circulation in biology I would think about the physics of it (fluid pressure, viscosity, etc) and also the chemistry of it. Within each subjects I would also try my best to relate the major concepts.
When I read an idea, I think about it and make sure I really underestand it. By that I mean I can do more than just the problems, but I know how to manupilate the concept, the consequences of changing minute details of it, etc.
All in all, just think about the material constantly until I get a near-intuitive feel for the problems. In physics and chemistry especially, when I read a problem I have a feeling of how this chemical or this system is going to behave given the conditions. It serves to double check my calculations and help me guess the right answers when I'm lost.