• Waiters/Waitresses: 15% - 20% for average - good service, more for exceptional service.
  • Headwaiter/captain: May get a cut of table server's tip; so tip your server extra to reward captain, or tip captain separately.
  • Bartenders: $1 - $2 a round -or- 15% to 20% of the tab, with a minimum of 50 cents per soft drink, $1 per alcoholic drink. If you tip well, and have more than 2-3 drinks, you'll probably get a "buy-back" - a drink on the house - as a reward.
  • Cocktail Waitresses: $1 - $2 per drink
  • Sommelier or wine steward: 15% of cost of the bottle
  • Buffet Servers: At least $1 per head if you get your own beverages. If you order beverages (or more) from the server, then you should tip 10-20% of the bill based on service quality.
  • Coatroom attendant: $1-2 per coat
  • Room Service: 15% - 20%  (However, if a tip is already included in the bill, you may forego the tip or tip lightly as an extra thank you.)
  • Valet Attendant: $2 - $5 average for each trip to the car; more may be appropriate given conditions (like weather or location).
  • Pool Attendant: $1 - $2 for each service (e.g., providing towels or lounge chairs).
  • Showroom Maitre d': $1 - $2 for preassigned seats
  • For unassigned seating, you may tip according to where you want to sit (usually a tip over $50 will guarantee your seat)
  • Washroom attendant: 50 cents to $1
  • Taxi driver: Varies depending on locality. Assume 15% will be enough; an extra $1 to $2 for help with bags.
  • Food delivery person: The Greater of 10% of the bill or $2.00. Should tip 15%-20% for a difficult delivery.
  • Grocery loader: Check with store policy if tips are accepted. If so, $1 for bringing bags to car; $1.50 to $3 if you have more than 3 bags.
  • Barber: 15% to 20%, minimum $1, for a haircut. For other services (shampoo, shave or manicure) tip $1 to $2 to service provider.
  • Hairdresser: 15% to 20%. (It is acceptable to tip owner, unless he or she says otherwise.)
  • Shampoo person: $2 or more
  • Manicurist: 15% or more
  • Spa service: 15% to 20%. If service is provided by owner, no tip.
  • Coffee/food retailers w/ tip jars: Tip is optional.
  • Handyman: Tip is optional but frequently expected.
  • Gas attendant: Tip is optional.
  • Skycap at airport: $1 per bag if you check-in curbside; $2 per bag if skycap takes bags to check-in counter.
  • Hotel doorman: $1 per bag for help with luggage; $1 per person for hailing a cab.
  • Hotel bellhop: $1 per bag for bringing luggage to your room (but a $2 minimum if you have just one bag)
  • Hotel housekeeper: $2 - $5 per night.  Customary to leave on the nightstand with a note such as, "To Housekeeping:  Thank you!"
  • Tour guide: $2 - $5 per person in your party. But, first inquire with the tour company whether tips are included in the cost of the tour.
  • Hotel concierge: $5 for getting you tickets or reservations ($10-plus if they're hard to get). No tip required when you ask for directions, suggestions for restaurants.  But if they make a reservation for you at the restaurant, they would appreciate a nominal tip.
  • Cruise: Varies. Ask cruise line about customary gratuities.

The general rule is that you do not need to tip on tax. Most people just look at the bottom line (tax included) and just tip on that.

 A great video for how much to tip in NYC and the rest of the  USA: http://www.slate.com/articles/video/h...