Got A* in History and A* in Economics (100 UMS).
The one thing I can perhaps put forward is that Set the foundations with a lot of revision for the mocks. You don't have to start revising now, but just make sure you have solid notes/knowledge for the mocks. Make it an aim to achieve an A in them. As once you have that you can work towards increasing your skills from that A to an A*, which from Jan/Feb to June is achievable.
For history I first learnt the whole syllabus. Condensed the syllabus into notes providing a summary of the key events during the period. I then made essay plans for literally every single question that had come up from every past paper and questions that could come up. I then pretty much did every history paper since around 2009 (start of new syllabus), got teachers to mark them and identify what I could do better, and kept applying advice on each paper I then did. For the coursework I put in a lot of work so it followed mark scheme and read well. Honestly don't cut corners with coursework as if you go into exam with 90+ UMS in coursework you make life easier for yourself.
For Economics, I wrote notes on the whole syllabus. Copied and learnt every diagram possible for essays. Wrote plans for every single essay question that could come up. Also looked at model essays and mark scheme meticulously to get a general structure I could use for any question. Then learnt everything and started doing essay practice, which teachers marked and gave feedback on each time. I honestly really struggled with micro (half the course) all year (we had change of teachers halfway), and it was only 1-2 months before exam I understood everything. I wouldnt worry too much if you struggle with 1 topic of a course, just make sure you go out of your way to really get to grips with it when exam time comes, no matter how frustrating it is.
Think I managed to get 100 UMS in Economics as i went to outside lectures at Cambridge/London and really read outside syllabus (newspapers, economist, academic articles etc), so referring to really high level stuff in exam gets credit as well. Did the same with history by reading loads of historic articles and getting some nice terminology in.
If youre going to take anything from this I would say, learn what mark scheme is looking for, go out of your way to make your answers distinctive from other candidates (read extensively) and learn actual syllabus inside out.
Hope that helps