Revise hard, see/email teachers if you don't understand something. I really don't understand split ring commutators in physics, so I just learnt a paragraph explaining how they work off by heart so I could write that if asked to explain them in the exam. That worked really well as I got the marks for that question in my mocks, without actually understanding the topic. Do lots of past papers to get a feel for what the questions are asking of you, and to practice time management. Good luck, passing all of your subjects is what is really important.