1. Don't rush yourself, take your time.
2. Make your radio calls early, this way you give yourself more time to concentrate on approaches, etc., also if you get a negative response you will be able to plan for an alternate easier.
3. Listen carefully to what your examiner is saying, don't be afraid to ask him / her to repeat their instruction.
4. If you are unhappy with something you are doing, exercise good airmanship and explain what you are doing to resolve the issue.
5. Don't second guess the examiner.
6. Remember, they are not setting out with the intention to fail you. They will make an allowance for nerves, but you wouldn't be doing the test if your FI didn't think you were up to it.
7. Let me know how you get on.
Good luck