Get books on programming, read, practise, read more, practise more, read even more, practise until you pass out, and so forth.

I'm serious about practising so much. I didn't practise in the first semester and now at the end of the second semester I still barely know how to program. We need to make an Angry Birds clone thing before next week Monday, but I really haven't a clue what to do and even if I skip every lesson and learn/work 24/7 the following week, there's no way I can ever finish it, so I've just given up on it. All the fault of my fucking laziness. Even now I'm slacking off.

Anyway, you'll probably learn Java at uni so get some books on that.

BUT BUT BUT: you don't actually need to know anything about programming before uni (at least not in Belgium), so as long as you pay attention in class, read and work a lot you shouldn't have any problems.