When passing through double doors, what is the etiquette for thanking the person in front of you for holding the door? Do you have to say "thank you" when they hold the inner doors and "thank you" again when they hold the outer doors?
Moderator's Note: Suggestion: Say "thank you" at the first door and then lunge for the second door to provide them the same courtesy they showed, saying, "My turn." But if by chance you're not quick enough, say "thank you, again." What's the harm in showing double the appreciation?