Start early! This is the simplest piece of revision advice there is, yet so many people overlook it. The earlier you start, the easier it will be to go at your own pace so that you can revise thoroughly. If you wait until the last minute you won't get everything covered.
Try several different revision techniques e.g. spider diagrams, pictures, flowcharts. Using colour and/or underlying words can help you to remember information more easily. The most important thing is to find an approach that works for you and stick with it
Don't revise late into the night the day before an exam. You might think it's worth it, but your concentration will plummet in the morning.
Don't revise for hours on end without a break. Your brain needs time to absorb and process what you've learned, so after every thirty minutes of revision, have a five minute break.
If possible, look at some past exam questions. Quite often, the same questions come up on exam papers year after year. If you look at the mark schemes, you can find out the answers examiners like to see written to certain questions. Using this method, you will also notice that there are only a certain number of different questions you can be asked on a topic. The more past questions you look at, the less likely it is you'll get a question in your exam that is totally unfamiliar.