I do aqa but firstly understand all the content maybe watch yt videos and look back at notes. Then memorise key stuff. The easy way I memorised stuff was by doing countless exam questions on the topics and looking at mark schemes. The questions are very repetitive and so is the mark scheme so write down stuff that keeps appearing eg. How mass spectrometry works? Once you’re comfortable with all the topics start doing past papers initially if you want to them open book obviously not looking at the mark scheme but ur notes and flash cards, then start doing them properly in exam conditions. When doing past papers if u come across any topics you’re not comfortable in or forgot repeat the steps again. What I do is I collate the main topic questions that reoccur countlessly and stuff I just keep getting wrong and put them in a ppt. Hope all this helps and all the best to us!!