Be -
Punctual,
Polite,
Smartly Dressed.
Attentive.
At the end of the interview when they ask if you have any questions, make sure that you have at least one - it shows that you're interested (I suppose to fly all that way for an interview you must have some interest anyway).
DON'T ask about your wage, or time off, or job perks - ask about when will you hear about the result of the interview, or ask about the opportunities for progression within WDW. If the question that you want to ask has been covered during the interview, ask if they can just clarify a couple of points.
Finally, be yourself. Don't try and come across as someone that you're not. Anyone that interviews for a living will see straight through you.
Good luck
