1. Meet with and get to know your profs. From my experience, that can make or break the outcome of your final marks. If they know and see that you are working hard (particularly if its a course you are struggling in), they are more likely to give you breaks and help you out.
2. Don't procrastinate. Sounds simple, but its easy to do. Get started on assignments right away, and try to plan having a few days to step away and have a last look before submitting.
3. Study your notes from each day and from there ask questions if you need something explained further. It will make exam time a heck of a lot easier!