Reading, reading and reading. Make sure that in coursework and exams, you don't just regurgitate what you've been told in lectures.
Plus... Look for the quick wins. Sometimes it's the small details which make a lot of difference when added up over two or three years. Anything that will earn you more percentages for just a bit more effort. For example, referencing is easy money and worth getting the hang if. All you have to do is follow the rules your uni uses and pay attention to detail. Not only is that a path to extra percentages, but it lends your work credibility and will make the marker(s) more positive about your work when they start looking at it.
Another thing which will do that, is making the work look neat and tidy. Follow your uni's formatting guidelines if there are any - pay attention to the font, the font size, margin sizes etc. This is especially important in the dissertation, where marks can be deducted for not following the format and presentation guidelines. Also, have a checklist of what sections the diss should include and make sure they're all there. If the guidelines say you should include a title page containing specific info, an abstract, table of contents, acknowledgements etc., then all of these should be there and marks will be deducted if they're not.
TL DR - Read around your topics, pay attention to detail, make sure you follow any instructions you're given. (NB This is not an exhaustive list!)