At this point it's probably best not to focus too much on setting incredibly high standards. I personally think you need to work out whether you'd rather a spread of mostly As and Bs or go for an A* in a few subjects and be happy to accept whatever you get in the other subjects (whether they end up As or Bs).
Once you've worked out whether you want to revise each subject equally or concentrate on a few specific ones, you should break down the time available into revision slots and allocate them to your subjects. Make sure you give yourself a few breaks, or you won't absorb material as effectively.
Then, before even starting any revision, gather all your books and notes and work out which material from each subject you're going to look at, any topics you need to focus on.
Above all, be strategic. Look up which topics you can bank on coming up in the exam based on past papers, and look at topics that you struggle with and could throw you.
Good luck!