I did mind maps, going through every lesson I've had condensing my notes and adding bits from my revision book. Afterwards I'd highlight key dates/names I'd also add some quotes from historians on the back of the map. They say the best way to test your knowledge is to teach what you've learnt, rather than put my parents through that torture I used to just present my mindmaps to myself, it helped me make links between the information and create my own opinion about the signifance of an event/person. It would also be useful to look at the exam board specification for the subject. If you type your exam board into google and find their history a level page it will give you an idea of the kind of factors/themes they'll be focusing your exam on. For example, my essay Q we're always either on economy, foreign policy or social or political factors. Therefore I made a broad essay plan for key points under each factor for every topic. As everyone has said essay writing is really important, not only will it make your stress less on the day of the exam as you'll have figured out a structure that works for you but it is likely that an essay you do for revision may turn up - it happend for me in AS. Oh and this is just what I did when writing essays, something my teacher suggested to the class, that you leave space to write your introduction and go back to it at the end. Often people contradict themselves by writing one thing in their intro then when discussing the facts reaches an entirely different conclusion. Anyway good luck for your exams, history is really hard so make sure you start revising early, though don't overhwhelm yourself.