Before you start revising, get all your notes sorted, and, draw up a list of all the topics you need to cover. This serves two purposes: you will definitely cover everything you need to cover, and, a bit of tidying and sorting out is a nice relaxing way to ease yourself into the revision process.
Plan exactly when you are going to revise and be strict with yourself. Don't just wake up one Saturday and say that you are going to be revising all day, because you probably won't get a lot done. Say that you will work from 10 until 11, then take a half hour break, then work until 12.30, then have some nice lunch, then do another hour, then go for a walk, and so on. If you are only revising in small chunks, and if you know the next break is just around the corner, your revision is likely to be much more focused and effective.
Give yourself little treats and things to look forward to. If you do a good day of revision, take the night off, watch some telly, go and see your friends, put all thoughts of Maths and school to the back of your mind. Buy yourself some chocolates, but only let yourself eat it once you have achieved what you need to do.
Don't just read through the textbook! The only way to revise Maths is to DO Maths. You will do much better spending 20 minutes doing Maths questions than spending 2 hours just reading a textbook. The more questions you do yourself, the more you will get right, the higher your confidence will be, the more you will enjoy your revision, and, the better you will do in the exam.
Use the internet. The internet is like having your own personal teacher who is available for you whenever you like. There are websites that can set you questions and mark them for you, take you through step-by-step how to tackle certain topics, and use fancy illustrations and animations that might just make that really annoying topic finally make sense. There are free video and audio podcasts that you can watch on your computer (or even iPods) which is like having a Maths lesson in the comfort of your own bedroom, or in the park, or wherever you choose. They can be started, paused, and, watched as many times as you like until you've got it! There are Maths games which you can play to practise crucial skills in a more fun way. All this stuffs is out there for you, so use it!
Don't just practice the topics you can do. If you are really good at fractions, for example, it is very tempting to keep doing lots of fractions questions and then smiling as you keep getting them right. But unfortunately, the exam is probably not going to have more than one or two fractions questions. Although it can be painful, work your way through the topics that you struggle with, because it is much better to struggle on them at home, when you have time on your side and the answers available, than it is to struggle in the exam.
Make sure you ask for help. Again, once you are in the exam, you are on your own, but during revision, you centainly are not. If you are stuck on a topic or question, then ask one of your classmates, or your teacher, or someone at home, or look it on the internet. You can use the Ask NRICH forum where you can ask Maths questions and get really good answers very quickly. Don't suffer alone!
Practice doing questions under exam conditions. Get someone to pick you a set of questions from the textbook, or get some from a Maths website, and try doing them in silence, with no help, for a fixed amount of time. This will get you used to what it will be like in the exam, how fast you need to go, and, this is the best way of checking that you really understand a topic.
Practice using your calculator! Many people seem to assume that any question that lets you use a calculator is easy, and all calculators work the same way. Those people are wrong on both counts! All calculators work differently, and unless you have used yours for lots of different types of questions (Trigonometry, Pythagoras, negative numbers, indices, standard form, etc.), you might come unstuck in the exam. Find out if there are any problems easly enough to correct them!
If it works for you, try revising with a friend for a bit of the time. You will find that one of you understands one topic more, whilst the other is a bit of an expert on another. Just by explaining things to a friend, you will find that your understanding increases, and likewise, you might learn a different way of thinking about and understanding a topic.
Whatever you do, don't stay up all night revising the night before the exam. Your brain actually needs processing time to sort out all the information you have bundled into it during your revision, and, sleep and relaxation are the best way to achieving this. Late minute cramming only makes you stressed and tired and makes it harder to access all the information at the back of your brain. Finish revising at about 6 pm, have a really nice meal, and take the night off. Nothing will disappear of your brain, and all the information you need will be much easier to find in the morning.
Before you leave the house, make sure you have got all your equipment. The most important ones are calculator (this is like an extra part of your brain which only you know how to use!), pen, pencil, ruler, compass, and, protactor.
Be careful who you talk to before the exam. When I was at school, I had this friend who was lovely most of the time but when it came to exams, she was - how shall I say this? - an absolute nightmare! She was always stressed and panicking, and after talking to her, I was stressed and panicking too! I know it is hard to do, but maybe try and keep to yourself before an exam and just be confident that you have done everything you needed to do.
When you get into the exam and find your seat, it is probably going to be a good 10 minutes before the exam starts. Spend this time wisely. Don't look around and pull faces at your friends. Read the instructions on the front of the exam paper. Not only will this get your mind focussed, it might just also tell you something important. One of my best students once messed up an exam because he didn't read that sentence on the front of the page that said, "Question 12 is on the last page". Question 12 ended up making a difference from an A* to an A!
A lot of people struggle with the timing of exams. They either go too quickly and end up with about 40 painful minutes left at the end with nothing to do, or they do so slowly that they don't get a chance to finish. If you want you can see how many marks are available on the exam (it will tell you this on the front of the paper), and divide the total length of the exam by this number. This will tell you how many minutes you have per mark, and will then be a pretty good guide of how long you are supposed to spend on each question.
If you get stuck on a question, move on! This especially tends to happen at the start of exams when you are still a little nervous and your brain hasn't had a chance to warm up. Some people like to flick through the exam paper and find a question on their favourite topic, do that one first, and then go back to question 1. Whatever works for you, but please, don't waste a load of time on a weird question that is only worth 2 marks.
Read the questions carefully! I know everyone says this, but there is a reason. Maths questions, more than in any other subject, contain words which, if you don't spot them, can send you down the completely wrong path. Imagine if you didn't see the 'not' in this question: Which of the following shapes are not regular polygons? Goodbye marks!
Show your working. Again, I know everyone says it, but it is just so crucial! This is especially important the older you get. In GCSE, showing your workings can be over half of the total marks. And the beauty of working out is that even if you make a couple of daft mistakes, you are still picking up lots and lots of marks.
Check your answers at the end of the exam. I used to hate doing this in exams. You have put all that work in actually doing the exam, you have 10 minutes left, surely you deserve a break? But if you find one or two daft mistakes (and everyone makes them), that could make the difference between a grade or level, and those painful 10 minutes will pass a lot quicker if you are checking answers than day dreaming being in a Rock Band!
Use the beauty of Algebra. A lot of people hate algebra, but in exams, it is brilliant because you can easily tell whether you have got the question right or wrong. If you are solving an equation, just substitute the answer back into the question and see if it makes sense. If you are factorising, then expand your answer and see if you get the question. It's like having the answers in front of you!
When you walk out of the exam, don't listen too much to what others are saying. You always have the people who come up to you san say, usually in a manic high-pitched voice, "what did you get for question 7c?... I got 2.35776, but I think I should be 2.35775... what do you think?... what did you get?". That is not waht you need. Then there are the people who say they've done rubbish and messed it up, when you know very well that they have probably got 99%. Again, don't worry about others. Take a bit of time on your own, and then, when you talk to your friends, get them talking about something else apart from Maths - what's up for summer?