Make sure that you have completed some previous exam papers as part of your final revision under strict time conditions. Also remember to have the answers (or mark scheme) on hand, it's no use thinking that you have the right answers. Even the most able students will make silly errors when working under time pressure. You need to make sure that you concentrate enough to keep the silly errors at a minimum and also ensure that there are no gaping holes in your maths skills.
Take a good look at the previous papers, they are unlikely to provide sufficient clues for you to be able to "predict" possible questions for your exam. However, they will help you to appreciate how examiners phrase the questions and help you appreciate the spread of knowledge you require. The questions sometimes contain clues which will help you solve them - remember the sort of clues which crop up and look out for these in your main exam. It's no good only revising part of what you have learned in maths. If you want to achieve a good grade, make sure that you can have a good attempt at all questions (even if you can't answer the generally trickier later parts of the questions, the earlier parts should be straightforward marks in the bag).
Strange as it may seem, maths is actually one of the easiest topics to revise - provided that you have understood what you have learned and have solved lots of problems along the way to help you reinforce your understanding. If you have done this then your maths revision should consist of testing yourself by doing past papers, identifying areas where you've forgotten what it's all about, solving more problems in your weak areas and that's it! No strings of dates or foreign verbs or properties of elements in the periodic table to memorise. Whatever you do, don't fall into the trap of thinking that maths is so easy that you don't really need to revise at all or you'll be in for a big shock!
Always check your work. Sometimes you can end up with silly errors and not realise it unless you check that your calculations are correct and that the answer is realistic. Statistics questions are notorious for containing calculation errors as there are normally quite a few numbers involved which need punching into your calculator. It's very easy to miss pressing a key on your calculator which can result in silly answers like saying that the distance from the Earth to the Sun is 14 Km or quoting an average age as 230!
Always read each question thoroughly. Don't just think "I know what this is all about" and trample through the question in your hob nailed boots - as you're very likely to come unstuck or make silly mistakes.
If you do a bit of maths before you start the exam it will be a great help, even though not all questions will have the same number of marks, it is a good idea to work out approximately how long you have to answer each question. E.g a 1 hour 45 minute exam with 19 questions allows about 5 minutes per question - so the last thing you want to do is linger for ages on a tricky question when there are others you could be answering and getting lots of marks for.
Always write down your method of obtaining answers - put down all thoughts you think are relevant. Correct answers do not always attract full marks - On a question worth 6 marks, even if your final answer is wrong it's still possible to get 5 out of 6 marks for showing your method!
Be wary of rushing through the questions you believe you know well, as a simple calculation error can throw you into confusion and dent your confidence. In particular double check figures calculated when drawing graphs and re-read the question to make sure you are not drawing the graph of y = 2x rather than x =2y!
Always check the question for Units (minutes, Kilometers etc.) and make sure that you use the correct units in your answer - remember to perform unit conversions if necessary. Also remember that answers in £ are always to 2 decimal places!
When calculating with minus numbers always show your working e.g. 2 - (-7) = 2 + 7 etc. Even experienced mathematicians make mistakes by missing minuses - make sure you don't.
Whenever you see a right-angled triangle in a diagram, no matter what the wording of the question, immediately think tan, sin, cos and Pythagoras. Then read the question properly and use these tools to get the answer.
When "Diagrams not to Scale" or something similar is seen next to a diagram - this means that you are expected to calculate the answer and not measure the lines with a ruler or try to estimate.
If you can't see how to do any part of a question, miss it out, but leave a gap in your answer book in case you can finish it later. If you are still stuck and time is getting short, then try guessing - you may get lucky.
Wish you luck !
How did you feel after your last exam 
