INFORMATION

TIPPING IN USA

Tipping is a very common practice in the United States, because often the service is not included and therefore represents the most important item in the salary of some categories such as waiters.
In restaurants, 15 to 20% of the bill is generally left in restaurants. To simplify the calculations generally in New York you leave double the taxes which are 8.875%.
Sometimes in places crowded with tourists or for groups of people over five or six, the tip is added to the bill (sometimes in pencil) or explicitly mentioned, so be careful not to leave it twice! Some restaurants in their receipts suggest the amount in relation to their account and the percentages are generally 15%, 18% and 20%. This should not be left in fast food, self service and takeaway.
The barman is left one or two dollars per drink while taxi drivers the figure is 15 - 20%, to which are added any tolls of highways, bridges or tunnels that are apart. In hotels you leave 1 - 2 dollars each suitcase for the porters, 3 - 5 dollars a day for the waitresses (who sometimes leave an envelope in the room) and a couple of dollars for the hotel doorman, if he calls you the taxi. If the hotel is of a luxurious category, the staff expects something more. For tour guides 15% - 20% in relation to their preparation and availability.
For other services such as theatre staff and cloakroom staff, tips are not compulsory but are appreciated.

References

Gratuity (Wikipedia)
Tipping (www.nyctourism.com)
Gratuity guide: Rules for tipping in the United States (CNN)