Not sure how different South African schools are compared to yours, but it was quite a very important year here, since it basically determines whether you get into University or not. Best advice I can give is to focus hard on your studies, not to skimp on smaller assignments (very important, that extra 3% or so helps a LOT) and attend extra classes on the subjects you do the worst in.
And if you're dead set on a certain University degree, APPLY AS SOON AS POSSIBLE. I can't stress this enough, University admission is the biggest pain in the ass you will ever encounter and the earlier you get it over with the better.