Actually understand the courses and what the lecturers want from you. I worked my arse off for some courses and still did poorly just because I didn't get the course or understand what the lecturers wanted. Others I didn't do shit all semester because as soon as I flicked through the lecture notes I intuitively understood the topic and I did heaps well in them.
Also, for assessments, stick to and constantly refer back to the marking guideline or the the original question/topic. I don't mean that you have to keep quoting it, but if you keep it in mind and lay your assignment out so that it's easy for the marker to understand what section of the assignment falls under what marking category then you will make their job easier and you will do better. I've seriously gotten distinctions for assignments I though I would fail because I just did not understand what the lecturer wanted, yet I've walked away with those marks because I followed the marking criteria, even with my piss-poor answers.