I've been trying to get 6 hours a day, with weekends off. It sometimes works, but not often. Maybe I'll put in some extra tomorrow. But that would involve getting up earlier. Ah well. Anyway, I've found the two best ways to study (for me, anyway) are:
1. Do lots of questions. Lots and lots. From past papers, textbooks, the internet, wherever you can find them. Do them, then check your answer. If it was right, move onto the next one. If it was wrong, copy out or summarise the answer given, then come back to it later (like the next day). Try it again, and if you get it right, move on, if wrong, repeat process, until you get it right. If you have real difficulties with it, put it aside to show to your teacher during stuvac, or something.
2. And this is my preferred method: Get a past paper, and work through it like an open book test. Take as long as you like with it, but look up any information you don't know. Make sure every answer is perfect, containing all the information you think it should. Once its done, read through it again, and then, a couple of days later, do the paper as if it was real. When you're done, compare it with the 'perfect' paper you prepared earlier. Any information you missed out of the second one, write down in dot points like a summary, making sure you highlight really important stuff, because colour makes learning fun. Review these summaries often.
NB: don't do summaries for maths. They are useless. Just do the questions over and over again. Also, if you don't like writing essays, which I don't, write out plans instead. Outline what you would put into each paragraph, and then only write the paragraphs which sound hard. This is much easier, if cheating a little bit.
Well... that was a lot... sorry. Anyway, thats what works for me. If you don't know what works for you, you can give that a try, see how you like it. And I agree that study is fun!