I mostly went for the "get helpful parent to ask questions from revision guide a few days before exam" method when I did my GCSEs. That worked fairly well for me, I got 1A^, 8A*, 2A and 1B overall (the B was citizenship in Y10, which was 60% coursework that I
just scraped a C in due to not being in most of the lessons) though I didn't really deserve it in all honesty. That was all very well when my UMS didn't matter, but I'm aiming for 93%+ in all my AS exams so I've had to raise my game a whole lot this year, which hasn't been fun... you're definitely right to start the hard work in Y11, then you'll probably have more in the way of study skills by AS than I had, which should be a real advantage when you get to it.
One notable exception to my rather laid back approach was French - I got the helpful parent to regularly test me on vocab in the weeks leading up to the exam, and to improve my listening I found an Alcest (a French band) interview on Youtube which was in French with English subs, and saw how much of it I could understand. I can't stress enough how helpful that was - because it was with native French speakers it was at normal speed, so when I went back into lessons my brain was used to a much faster pace than the practice listening tests we were doing, and I could just understand it all effortlessly. I'd suggest trying something similar for your Spanish.
For Music (AQA) I got an A because coursework dragged me down, but I got full UMS in the exam through a combination of relentless practice of past papers in class and good questions coming up on the real thing. I also went on the Bitesize site the weekend before the exam, but that wasn't any help as my course content wasn't the same as the material they had on there.
In Geography (AQA A - ask me anything if you like) I scraped my way to an A* through getting a re-mark of the physical paper. It is so so so important to learn your case studies inside out, and everyone will tell you that, but it really is essential. Another specific point, which I think let me down a bit, was that you should be aware that they can throw in the exact same case studies you've studied, so if you've covered two that work for the exact same area of the course, choose your favourite to learn in depth, but also go over the main points of another one just in case. In my physical exam, we'd studied the Boscastle floods in class, which I learnt, but then there was a whole section in reference to that on the exam and I didn't have anything else to talk about, so it looked like I didn't have any knowledge other than that given in the question.
I also did AQA L2 Certificate in Further Maths, and I saw it as just a bonus since I knew I'd already got a very high A* in GCSE (this was when you could sit exams in November, as I did the very last modular entry exams for Maths). So I did no revision at all outside of school, but they made us come in for maths lessons even though we'd finished every other subject, so I suppose I revised for this by doing past papers, which is what we did in class. As you've probably guessed by my grades (above) I got an A^ in this.
So anyway, I'm taking all maths based subjects now, and what I've found works best for me is literally just doing past papers, marking them (harshly) and going over things I don't understand, so I'm learning not only the content but the exam technique as well, and I'm not wasting time and getting bored going over things I already know inside out. We'll see in August how effective this method actually is (and I really hope it works!), but 'traditional' revision bores me to tears, whereas I see exam papers as exciting challenges, so it makes studying bearable for me. The one cautionary point I would make is that you shouldn't do a whole load of them in one go, then mark them all at once, as this is just wasting the finite supply of past papers there are available. Mark each one after you've finished it, look at the topic areas you've dropped most marks on, and then go over that content again, obviously being aware of what was a stupid mistake and what was genuine lack of understanding. That way you get to compare your marks and see how you are improving
I'm sorry this is very long and excessively verbose. Good luck with your revision and I hope you get all those A*s!
*EDIT* Forgot to mention, for any bits of content I need to stick in my brain, I've made a few simple posters with felt tips, nothing artistic, but decorative enough that I'll read them. Great for definitions/bond angles/trig identities etc!