Hi,
Did mine back in June and was advised on the following before I took it.
1. Take your time
2. Be thorough on all your flightplans/met/notams/W & B etc. then sit the examiner down and take him/her through everything in detail. Let them know that you know your stuff!!
3. Explain what you are doing
4. When (not if, in my case) you make an error (and realise it) tell them.
5. Remember the words your instructor has said to you throughout all the various exercises - let them talk to you in your head
6. Finally, tell yourself to relax and enjoy it
Good luck