As far as I know, Miami Beach is the only city in the U.S. where it is customary for restaurants to add the gratuity to the check. Waiters call the practice, tagging the check. They're hoping you don't see the added gratuity, and you mistakenly double tip them.
I'm sure the reason for adding the tip has to do with the large amount of European and South American visitors to the City.
But in opinion, this leads to lazy, bad service. I've seen many waiters who don't give a darn if you're having a good time because they know either way, the tip is included.
Most of the upper-class restaurants do not add a tip, but make sure to check your bill just in case.
If you have ever wondered who and how much to tip? Consumer Report has some advice for you:
"While 93 percent of survey respondents said they tip the bellhop who escorts them to their room, only 69 percent leave anything for the chambermaid who cleans it. But both should be tipped. Leave $2 per person each day for the chambermaid. To make sure the right person gets the money, don't leave a lump sum on your last day."
Here is more tipping advice from Dr. Dave & Dr. Dee:
At the Restaurant:
Maitre d': $20 or more, if a special service is performed such as getting you a table when you have no reservation and the restaurant is full.
Waiters: 15-20% of the bill, unless a gratuity is already added to the bill. In the United States normally a gratuity is not automatically added unless you have a party of 6 or more. In a buffet restaurant, add 10% to the bill for gratuity.
Sommelier (Wine Steward): 15% percent of the bottle price
Cocktail Waitress: 15% of bill or $1 minimum whichever is greater (i.e. if a drink costs $5, then 15% is 75 cents, but leave $1).
Bartender: if you are served at the bar, 15% of the bill, or $1 minimum, whichever is greater.
Coat Check: $1 per coat
Restroom Attendants: $0.50-$1
Musician in Lounge: $1-$5.
At the Hotel:
Parking Valets: $1-2 when you leave your car and again when they get your car.
Bell Hop: $1 per bag plus a couple extra if he shows you the room.
Doorman: $1 for hailing a cab; if he helps with luggage, same as Bell Hop.
Concierge: nothing for simple questions. But, if they make restaurant reservations, obtain theater tickets for you, make travel arrangements, then $5-$10 per task performed. Put the gratuity in an envelope with a note of thanks and give to the concierge.
Room Service: 15% of the bill, unless a gratuity is already added
Delivery to Room: if you requested something delivered such as a hairdryer: $1
Housekeepers (maids): $1-2 per day left at the end of your stay.
Spa Services: 15-20%, if a service charge is not already included. Ask that the gratuity be divided among the providers.
Swimming Pool Attendant: No tip for handing out towels, only if special service performed, then $1-$2.
Tour Guide: $2-$5 for a 1-2 hour sightseeing tour.
At the Airport:
Porters and Skycaps: $1 per bag
Shoeshine Person: $3-$5
Cab Drivers: 15% of the bill.
On a Cruise Ship:
Some cruise lines add the gratuity onto the payment for you, so check with the specific cruise ship on which you will be traveling. Otherwise, plan to include tipping as part of the cost of taking a cruise. Usually small envelopes are left in your cabin with suggestions for gratuity amounts such as:
Cabin Stewards and Waiters: $3-$4 each per guest per day.
Maitre d' and Busboy: $1.50-$2 each per guest per day. (Some suggest $10-$15 to Maitre d' for the week).
Hand out the gratuities in the envelopes to each person at the last evening’s meal, and to the cabin steward the day before the cruise ends. On a cruise ship, you don't need to tip your bartender, wine steward or bar waiter because a 15% surcharge has been added to every drink for gratuity. Some cruise lines may state “tipping not required”, but tips should still be given for good service. The link below gives tipping guidelines for different cruise lines.
if you're traveling abroad, check out what are the rules in different countries at Del Amo Travel.