Visualization, imagine yourself meeting the examiner, answering all show and tell questions, imagine reading the license plate, imagine yourself in the car what you would do as you drive down the road of the test centre if he tells you to go left or right what you would do, if you've been to the test centre before with your instructor you will know how it is around there a width restriction imagine going through it how you will place the car what gear you will be in how you will be making your observations, mirror signal maneuver how you will control the car so it is smooth.
Above all just smile and you won't believe this but if you imagine every scenario in your mind and put all you have learnt into some vision a couple of hours before your test, as your imagine it all beforehand, it can be so powerful, you become confident and so amazingly in control, keep smiling you will remain calm.