What subjects are you doing? I have different methods for all mine:
Mod. history Think of what you're learning more as a story, look at your notes for a few minutes, tell the story to the poster on your wall a few times, look at notes again to see what you missed, repeat...
German Make a list of new vocab you need to learn and carry it around in your pocket all the time. When you're on the bus/waiting at the train station/whenever look at them and learn a new word or two. At the end of the day, write a little 'diary entry' with all the words you learned and read the whole thing every few weeks to refresh your memory. Also good for languages - just think back to whatever you learned in school that day and try and talk/think about it to yourself in that language.
General maths Learn the formulas (stick 'em up somewhere or say them over and over till they're in your head) and then do loads of practise exercises. it's good if you have your own book so you can underline all the important info in the questions, which stops you from mucking up when it's a wordy question. Even if your teacher doesn't go through the book that often or set homework, do the exercises yourself. I like the structure of going through a textbook and knowing I've covered everything.
Biology You get sick of hearing it, but this one is all about the syllabus dot points. Teachers get your assessment tasks right off them, so if you've made your own summaries, you're one step ahead. Also there's a lot to remember, so make summaries as you go. Be concise.
English OK, I never really revised much for this. But here's a tip for your speeches - learn them. Even if it's just the start, a bit from the middle and the conclusion, because that's when most people pay attention. You'll be able to look around and make eye contact, which really impresses the teachers. My assessment was worth 30%, 10 marks were for how well you presented your speech and only 5 were for how good the stuff you'd written was. I got full marks because I'd memorised a lot of mine.
Geography I had an open book assessment - just read the textbook the night before and make sure you know exactly where the stuff you need is. Also, do a lot of practise on the skills based questions. Reading the theory isn't enough, you need to practise or it's easy to make stupid mistakes. When doing the case studies, make sure you know where they are and all the stuff about the biosphere, lithosphere, atmosphere and hydrosphere. Make notes in the form of a fact file and learn them!
Take the time to learn little tidbits when you can - on the way to school, when your parents are driving you somewhere, at the bus stop, in the adbreaks while watching TV, while you're doing the dishes, whenever. All adds up.
Hope that helped some.
And remember
don't procastinate! Then you'll have good habits sorted for year 12.