As much as I hate to say it, there's no 'special secret' to getting the grades. There's no pass code and no single specific routine that you can follow to magically achieve all A/A*.
That's probably a harsh way of putting it, and I'm sorry about that, but I do see a lot of people trying to find the 'one thing' that'll work, when in reality you really just have to get down and study. It's still early, but if you start revision now and start it properly (not just reading notes), then you'll probably be in with a pretty good chance.
Past papers, rewriting notes from textbooks and making flashcards all helped me a lot. Another big thing is ASKING YOUR TEACHER FOR HELP. If there's anything at all that you don't understand, even in the slightest, ask your teacher about it. I struggled with this for a long time but once I started doing it more in year eleven, it became really helpful. Their job is to help you learn, and they can't do that to the best of their ability unless you're letting them know what it is that you need help with. Towards exam time, one of my teachers actually used his free lessons to help me learn some topics that I didn't understand, and they actually ended up being some of the most important topics in the exam paper.
So start now, work hard, and good luck!