1. Don't wear your tshirt that says "iflyjets4food" When I did this in 94 at COEX the IAH CP wanted me to take it off because through my sweat in August under a white shirt, the pax could read it while I did the walkarounds.
2. Never pass up the opportunity to take a leak when you have 30 seconds.
3. If a pax comes up and tries to tell you that the carburetor is making funny noises on the engine (turboprop only), Let the Capt speak. Don't do as I did on IOE and start to make a stupid comment that "Actually, it is a turb..." when the Capt cut me off and politely thanked the man for confirming his fears that it was either the carburetor or possibly the timing chain, but it would be looked at thanks to his attention to the matter. Same if they say the muffler is making odd noises "in the beginning of the flight" on jets.
4. Drink some water during the day so you can do 2. above
5. Have fun!