I was predicted 2A* in Philosophy and History - just finished my finals a few days ago. For essay subjects, the important thing is exam technique... I know that sounds really lame but come the exam - you should know practically everything required (start revision 3-4 weeks before exam). Philosophy is just about learning the arguments for and against, and the exam technique is structuring these arguments in a logical way so that the essays you produce are coherent - a coherent essay that shows you know your stuff always scores highly. History is just a solid grind to get all the facts and figures burned into your brain, I can't speak for the exam technique as people do different boards that do vary quite widely. I did AQA, and it was just about making sure there was a clear argument in your essay - and that it had a clear conclusion. As for coursework... don't miss deadlines... what else is there to say? Pace yourself so that you have all your coursework material done (notes/research etc.) then begin the Coursework. Don't start before you have completed your research. For my coursework, it took 4 months to get all the notes down, 1 day to do the first draft, and 3 days to do the final thing. The essay isn't the problem with history coursework, it's the gathering and selecting of material. That's important to keep in mind.
The essays you do throughout the year should really be the prep' you need regarding exam technique. Try and aim for A's in the essays you do in class and for homework, because if your teachers are anything like mine were, they will mark ridiculously harshly so even a low A would probably translate into a solid A*. It's also not a bad idea to revise from the essays you do throughout the year, as if they get a good mark, you have a revision tool all ready made with the necessary knowledge and structure included. Make sure you look after these and indeed all the essays you do - make a folder on your computer and put all of them there, or, if they are handwritten - put them all in a separate ring-binder so you don't lose them.
I got 280/280 in History at AS level + A2 Coursework, in Philosophy I got 181/200 at AS. I obviously don't know what my results will be, indeed in Philosophy for one point I stated the wrong Philosopher (they both began with G's =[ ) and for one of the questions I'm worried that some of the points may not have been entirely relevant to the question, but the important thing is to look back and have no regrets.
Revise hard come crunch time, look after the work you do in class (and at home), participate in lessons, and ask your friends for help when needed. If you do these things, you know you've done practically all you can to get an A*.