Although I'm not doing AQA History, I have been doing OCR History for 3 years so I can recommend some general study resources that helped me. One revision tool I find particularly useful for achieving high grades are past papers and past paper questions- you can usually find lots of them online,or if you want some questions relating to what you're currently studying I would recommend asking your teacher. However this is more for revising in the future when you have actually started your course, if you haven't started your course yet and just want to get ahead learning the knowledge, I would recommend using any revision guides you have available and the internet (I find Bitesize particularly good as well as Youtube videos) .
As for what to do now, I honestly wouldn't worry that much about studying the content before starting the topics properly, even if you're aiming for grade 9's. I would recommend just focussing on relaxing as much as you can whilst you can and if you really want to do any extra work, only doing enough to get a basic understanding of your courses.