This article will help you understand when, how and what to revise.
First you need to determine when you are most awake (an excellent time to revise) and when you are most sleepy (obviously a really bad time to revise!).
Head over to http://www.bbc.co.uk/science/humanbody/sleep/crt/ and answer the 4 questions, you will get a chart which shows you at what time of day you are most alert and most sleepy. Take note of the times when you are most awake.
Now you need to create a revision timetable, you can either create one yourself, ask a teacher or progress coach to help you create one, or you can use TSR's Study Planner: http://www.thestudentroom.co.uk/g/planner (You can also find this under 'My TSR > TSR Apps' on the blue nav bar). The Study Planner will help you to prioritise your weaker subjects, and will let you know how you're spending your time so you can see what subjects you need to focus more on.
The GetRevising website is free to sign up for, and you can prioritise your exams, so you can be confident that you will revise adequately for each of your exams. You can also find all the Get Revising resources on TSR: http://www.thestudentroom.co.uk/learning.php
Once you have your revision timetable, you need to decide how long to spend revising for each exam. If you are like me and find it hard to concentrate for a long time, then commit to 30 minutes per exam (this will work out to 2 hours per day). Obviously if you have the ability to concentrate for hours on end, then commit 1 or 2 hours to each exam (this will work out to 4 - 8 hours per day). The key point to this step is to allow yourself enough time to learn, but not to spend so much time that you get distracted, or cannot be bothered to revise every day.
So you now know when and what to revise, now you just need to know HOW to revise!
Different techniques work for different people. I suggest you read through your revision guide and class notes, and either write down the key points in a note book, record yourself reading out the key points, or even draw pictures and diagrams if that is how you learn best. The important thing for you to do from now is to stick to your revision timetable, you will be amazed at how much you get through if you just sit down and study without any distractions!
After a few months, you should have gone through all of your syllabus, and have a nice collection of notebooks/voice recordings/diagrams.
Now you need to commit these to memory, there are various ways to do this, if you have already found a technique which works for you, then use it!
I recommend using flash cards. Make your own to memorise the key points.
You could also read through your summarised notes, cover them, and see if you can recite them out loud. If you have recorded you voice, then you can listen to the key points and attempt to recite them out loud as well.
One month before the exam, keep doing past papers and questions if they are available, this will help you find any gaps in your revision, use your summarised notes to fill these gaps!
Good luck for your exams! Start NOW and not 2 months before your exams, 2 months might sound like a lot of time, but you want to completely master each of your subjects!
It should take you around 2 - 3 months to complete the syllabus, about 1 month to commit your notes to memory (this depends on how good your memory is!), and 1 month to go through past papers and "patch up" any gaps in your revision.