According to
Emily Post, the following is 'correct etiquette':
General Tipping Guidelines
When and Where and How Much
RESTAURANTS:
Wait service (sit down)
15-20%, pre-tax
Wait service (buffet)
10%, pre-tax
Host or Maitre d'
No obligation for greeting you and showing you to your table.
$10-$20 for going above and beyond to find you a table on a busy night or on occasion, if you are a regular patron
Take Out
No obligation
10% for extra service (curb delivery) or a large, complicated order
Home Delivery 10-15% of the bill, $2-5 for pizza delivery depending on the size of the order and difficulty of delivery
Bartender
$1-2 per drink or 15-20% of the tab
Valet
$2-$5
Tip when the car is returned to you.
TRAVEL:
Skycap
$2 first bag, $1 per additional bag
Doorman
A smile and a "thanks" when he opens the door
$1-$4 for carrying luggage
$1-$2 for hailing cab (add an extra $1 if it's raining)
$1-$4 beyond the call of duty
Bellhop
$2 first bag, $1 per additional bag
$2-3 for each additional service, such as room delivery
Housekeeper
$2-$5 per day, left daily with a note marked "Housekeeping - Thank you"
Concierge
No obligation for answering questions
$5-10 for tickets or restaurant reservations
$15 for hard-to-get tickets or reservations, or 10-20% of the ticket price
Taxi driver
15-20% of the fare, but minimally $1
$2 for the first bag, $1 for the second
SALON/SPA:
Hair Salon
15-20%, ask to be split among those who served you
Manicurist
15-20%
Facial, waxing, massage
15-20%