OCR is a...at A2, it's much tougher!
I understand your hate for AQA, they are ergh. I'm put off Biology because of the exams are so random! I heard AQA Chemistry is easier than OCR but that is subjective. Anyway, my advice is to:
-Learn all definitions thoroughly, this is the easy marks. Can easily boost you up a grade or two! You need to get every mark you can get!
-Go through the specification and where there's points such as 'state that a nucleus is surrounded...' just LEARN it. Sometimes in the specification, the answers are right in front of you and you need to be able to recite it exactly how they want it. Unfortunately this makes your grade at the end. With OCR it's easier because they do have a detailed specification whereas Biology's specification is terrible (IMO).
-Past papers are your best friends in Science & Maths subjects. They will make your grade, examiners can only ask so much so once you've covered every single paper, you honestly shouldn't get below a B grade. But saying this, you need to be able to understand the concepts as you will need them in A2. This also requires a lot of time so you should start past papers this week really on topics you've covered.
-Use CGP/Revision guides, they make life a lot easier (and sometimes entertaining). Refer to the CGP along with the specification.
-Read Examiner's Reports, they are telling you what students mess up on and that's something that is so important because there's a high chance the examiners will test it again! So read them, highlight them, analyse them!
Hope that helps