Revision techniques can work differently for different people but the main way to succeed is to plan. First of all, try to figure out how you retain information best and structure your revision round activities that work with your learning technique. Eg if you are a visual learner, use flashcards, colourful pens and diagrams to remember geographical processes and structures. Then make yourself a revision timetable that includes all of your subjects. Try to balance your time well and if you feel that one subject has much more content to cover, start your revision in that subject first.
Geography GCSE has a lot of different modules and topics to cover which can be daunting, but they can be broken down. If you approach your revision in little pieces it is more digestible and you wont feel exhausted and defeated by it.