Most importantly, make sure you are ready to take your test!  Take advice from your Instructor, they have put many people through their tests, and know when you are ready.
You need to be competent and confident in all the skills required to pass your test.
You need to be able to assess any given situation and ‘adjust’ your skills to fit.
Be calm and relaxed – easier said than done!
Don’t worry about the Examiner taking notes.
Don’t worry about any mistakes you know you have made. 
Once done it is history and you can’t undo them, so make the best of the time left to show the Examiner your skills.
The test is to show the Examiner what you can do, not the opposite.
If on the test you feel you are losing the plot, ask the Examiner if you can pull over.
So that you can get yourself together.  Don’t be afraid to explain that you are nervous.
If you suffer from left/right dyslexia TELL the Examiner.
They will then indicate by signing left or right when giving instruction.