Make sure you explain what you are doing and why, especially when doing things like FREDA checks. Also my examiner asked me quite a few times where we were on the map so it's good to know!
When doing the diversion, remember that your heading and time estimate can be changed if things aren't panning out as you expected, but tell the examiner. He won't mind if you say 'I think I will be there at 40 instead of 30', but he won't like it if you just arrive at 40 having told him 30.
Also make sure you are well rested - my skills test lasted 2 and a half hours and I was absolutely kn**kered afterwards.
Easy to say, but try and relax - the examiners know you are nervous, and they do make allowances - even if you do something wrong, carry on and don't think 'Oh no I've failed!'
Good luck!