Just a thought from chatting with my examiner and others...
Make the effort to appear professional - look smart, be on time, don't smoke, be clean, no BO, etc. - usual job interview type rules.
Doesn't mean you ll pass if your flying is crap but who would you trust with your family - professional smart pilot or someone in torn jeans and t -shirt?
It maybe wrong but image DOES count...
PW
PS. If you re going to wear smart shoes make sure you fly in them before checkride as pedals, (certainly in helicopters), feel different in shoes to trainers! Been there got t-shirt!