Tipping is more common in the United States than in many other countries. Tips (also called service charges and gratuity) are not usually added to the bill in restaurants or hotels but are often expected and needed by the employees. Their income is lower because tips are considered to be a part of it. Restaurants will often add the tip to the bill for large groups, so be sure to check the bill closely when dining with five or more people. If a service charge was already added, you do not need to add any more.
Bartender: about $1 per drink or 15%-20% of the tab
Food delivery person: the greater of 15% or $3
Hair dresser (or for any type of spa service): 15%-20%; if someone else shampoos your hair, it is typical to leave an extra $2 for him or her
Taxi driver: about 15%; an extra $1 or $2 if they help with luggage
Valet attendant: $2-3
Hotel housekeeper: $2-5 per night
Hotel bell hop (the person who carries your bags to your room, at some hotels): $1 per bag; $2 minimum
You do not tip anyone in a cafeteria, motel, or in any place where you provide your own service. If you hire movers, tips are optional but recommended.