You are on travel to the U.S. and do not know how much you should tip? Jacqueline Whitmore, an etiquette expert and founder of the Protocol School of Palm Beach published her guidelines for travelers.
In Airports for example taxi drivers are supposed to get 10 to 15 percent of the bill and the car service 20 percent of the bill. At Hotels you should pay the doorman $1 to $2 per bag for moving your bags from the car to the bell cart. The room service gets 15 to 18 percent of the bill before taxes.