Well for starter is to learn meditational skills to calm your nerves. Start revision 10-12 weeks before exams that would lessen your anxiety in exams as you know that you are fully prepared. Also check out exam solutions it gives a step by step answer to exam questions in video form.
A week before your exam think about the setting you'll take your exam in whilst doing something calm, maybe watching a funny TV show or even yoga. Just take some deep breaths and think about what you will do on the day. (You'll do great)
Revise more gradually as you get closer to yourself and before you go into the exam remind yourself that you know everything you need to know for the paper.
When you get into the exam room take a moment to empty your head, if it helps imagine you are back in your Math class doing a mock or somewhere where you don't feel pressured.
Flick through the paper to see what questions are there, know which questions will take longer according to their marks (4 mark question will take longer than a 2 mark etc)
I am sure your exam wll go great, just be calm and revise. Good luck (: