At Restaurants: The gratuity isn't included, so tip the standard 15 to 20 percent, depending on the service.

At Hotels: Concierges who go out of their way for you should get $10 to $20 per favor; porters get $1 or $2 per bag; housekeepers $2 a day, or $5 in a luxury hotel. "Leave something for them daily," advises Mary Pyle Peters of Distinctive Journeys in Blaisden, California, which organizes USA trips. The person who cleaned your room all week may not be the same one who comes in the day you check out.

Guides and Drivers: Tip them collectively 15 percent of the cost of the excursion. Taxi drivers get 10 to 15 percent.

Dollars Accepted? Yes. "As long as you use paper money, not U.S. coins," says Peters.

Source : CNTraveler.com