Tipping also can be stressful for the customer. Whether you find yourself in the hustle and bustle of a busy airport or in the placid stillness of a cruise ship cabin, tipping customs can vary.

When should you tip? How much? To whom?

Restaurants

For waitstaff, 15 percent of the pre-tax bill is considered standard. Twenty percent is not unusual for outstanding service. Some restaurants add a 15 percent or more gratuity to the check, especially for large parties, so look before tipping. Bartenders typically receive 10-15 percent of the bill; wine stewards, 15 percent; coat check, $1 per coat; valet parking, $2-5.

Hotels

Housekeeping staff are often forgotten because they work while you're out of the room. For stays of more than one night, $1-$2 per person, per night is standard. The tip should be left in the hotel room in a marked envelope.

Bell staff traditionally receive $2 per bag; room service waiters, 15 percent of the bill; the doorman, $1 for hailing a cab. To ensure special treatment, you may consider a $10-20 tip on arrival to the concierge or a $5 tip to the bell staff.

Airports

In the loading and unloading zone, the skycap generally garners $1 per bag. The same goes for shuttle drivers who are transporting you from a nearby parking area. Taxi drivers get 15 percent of the total fare or $1 minimum.

Cruises

Some cruise lines have a "tipping not required" policy. This does not apply to services rendered off the ship. And, of course, it does not prevent you from rewarding hard work. A cabin steward generally receives $3-$3.50 per person, per day, and the same goes for the waitstaff. Also offer a gratuity to the Matre'd, head waiter, wine steward or other service staff who have provided good service during the voyage. Tips are usually presented in person, in an envelope at the end of the cruise.

Gratuities are always appropriate for the tour guides on shore excursions. Tips of $5-$10 per person are customary.