While tipping is NOT mandatory in most of the United States, it is expected in many circumstances for service, especially at almost all sit-down restaurants which offer table service. 

"Suggested tips" and "further insights, discussions, and recommendations for tipping" below may represent what Americans who work in service industries feel are fair tipping practices

Following is a U.S. tipping guide prepared by U.S. News & World Report staff: 

http://money.usnews.com/money/persona...

Here's one tipping app for smartphones and tablets:  Globe Tipping.

Many visitors to the U.S. feel pressured to tip even when they do not feel it is fair or reasonable to do so.  Customers cannot be forced to tip as a matter of law, but they are legally required to pay any charges that are clearly marked prior to service, and these may include mandatory gratuities (tips).  Mandatory gratuities are used by some restaurants with large numbers of foreign customers who may not be familiar with American tipping customs, often in tourist centers such as New York City.  Mandatory gratuities also are charged by many restaurants when large groups are being served.

A very few restaurants and restaurant chains may discourage tipping. There are a few U.S. restaurant chains with limited table service that discourage tipping when customers receive table service.  For those who prefer not to tip, but also don't want to deal with their own trays or the trays and drinks of children at fast food restaurants, these restaurants may offer an alternative.

Fast food restaurants do not have tipping, nor do they have table service.

Obviously at restaurants with no tipping policies or where gratuities are automatically added to customer checks, there is no need to tip unless there is a desire to additionally reward some exceptional service.

Some coffee shops, bakeries and other establishments have tip jars on their check-out counters.  These have become more prevalent in recent decades and there is some confusion, even controversy about them.  Generally, those who feel a desire to reward good service will make a contribution to a tip jar.  Others do not.  Both are fine.

As explained below in greater detail, customers should understand that tips are often a major source of compensation for wait staff and other U.S. service providers.  Employers often pay these employees lower wages in anticipation that the service employees will receive tip income to raise their compensation to market levels  -- however, U.S. employers are legally supposed to pay all workers the higher of either the Federal Minimum Wage or their state's minimum wage.  Many of these employees also may be part-time employees and not receive any employer-paid benefits such as health insurance, which they consequently must pay for personally.  So customers may not be paying more for the service that they are receiving than if the cost of the services were built into prices as they are in many other countries.

Many hotel guests who tip housekeeping staff leave tips daily before leaving the hotel, both to reward the person immediately servicing the room and in expectation of good service.  

Suggested tips:

  • $1-2/bag for skycaps, bellhops, doormen, and parking valets if they handle bags, $1 per coat for coatroom attendants, $1 per diner at buffets, $2-5 per night for housekeeper, $5-10 for concierge (only if they arranged tickets or reservations), $1-3 per bag for grocery loaders (not in all areas of the US).  Doormen who merely open doors are not tipped, unless they call a cab or provide another service.  Parking valets are paid upon pick-up $3-5, depending upon much effort is required to retrieve a vehicle.
  • For waiters at sit-down restaurants, bartenders, barbers/hairdressers/attendants at beauty salons, taxi drivers, tour guides, and food delivery folks, the tip should be calculated as a percentage of your total bill as follows: 10% usually means you aren't totally happy, 15% usually means all was acceptable, 20% for excellent, over 20% for outstanding.  15-20 percent is considered standard in most communities.
  • For ski instructors, tipping 15 percent for adult groups and 10 percent for private clients is pretty standard. 
  • These percentages are highly subjective! 
  • Note that tipping percentages will vary in different parts of the country, and even in different parts of a state. Reportedly, tips of 25 percent may be expected at higher-quality restaurants in New York City.
  • Ignore sales tax when calculating tips.
  • Note that if you have more than one person serving you at these establishments, the percentage represents the total tip and should be split amongst all who serve you.
  • Tips should only go to people who are helpful. If they don't help you, don't tip them.
  • In some places a clearly displayed "Service Charge" or "Gratuity" might be automatically added to a bill, especially for party sizes of 8 or more. Check your bill for these charges before tipping.  If the word "Gratuity" is used and you're not happy, check with the manager.  A gratuity by definition is an amount you don't have to pay but choose to. 

(These recommendations are based on ones provided by the Emily Post Institute. For those who are interested in etiquette in the USA, most Americans refer to Emily Post or Amy Vanderbilt for the final word on manners.)

For further insights, discussions, and recommendations on tipping, see below:

Restaurants with table service: Tip 15% or more of the bill, based on the quality of service. If you receive exceptional service, 20-25% is customary.  In major cities of the U.S. however, 20% is considered to be a "good tip." Note: In most larger restaurants in the USA, the server has to pay back a portion of their tips to the bartender, busser, hostess, and food runners.  A good rule of thumb is if you see people other than your server helping maintain or clean tables, serve wine, or deliver food, those people are being tipped by your server for their work. Even if you do not see additional "support staff, it is vary likely that the server is paying a portion of their tips to other staff.

Please note that in *some* states, restaurants are allowed to pay their servers as low as $2.13 per hour. This base wage varies among states, for example, Massachusetts pays $2.63, Connecticut $5, and California $8. Service is almost never included in the bill. If it is it will say "Gratuity" or "Service Charge" with an amount next to it. If an amount is included as a "Gratuity" or "Service Charge," tipping is not required.

Unlike in most of the rest of the world, the total cost of table service almost always is NOT included in the bill, necessitating the need for tips.

The exception to this general rule occurs at some restaurants for large parties (typically six or more people).  If you're with a large party, be sure to check your bill just in case. 15% - 20% is often automatically charged for a large party (six or more).  If the tip is included, the breakdown of the bill will read "gratuity" or "service charge," which means that a tip is already included.  As always, if you feel you did not receive 15% service, inform the management before paying your bill and have it adjusted to the adequate amount.

A good rule of thumb when calculating a table service restaurant tip is to ignore sales tax, and, for good service, calculate 15% of the entire food, beverage, and wine bill.  (This is the amount listed before the sales tax line.)  Add 20% if the service was outstanding, especially prompt or friendly, or the server fulfilled many special requests.  Note: in most larger restaurants in the USA, the server has to pay back a portion of their tips to the bartender, busser, hostess, and food runners.  A good rule of thumb is: if you see people other than your server helping maintain or clean tables, serve wine, or deliver food, those people are being tipped by your server for their work.  In resort areas like Disney World, it is usually 3% to 5% of the server's total food, beverage and alcohol sales, so the tip should be adjusted accordingly.  At higher end restaurants, there may also be a sommelier or wine steward.  You should tip the sommelier separately, at your discretion.  However, in some restaurants, the server tips the sommelier based on their individual wine sales, so it is advisable to ask your server first.  Individual drinks you are served at a restaurant bar should always earn a $1-2 tip each. 

In most states, sales tax is applied to the bill and is clearly indicated as such on the bill.  In those states where the tax is 5% (Massachusetts as an example) or 6% it is simple to calculate the tip by rounding the tax up or down to the nearest dollar and then multiplying by three. 

It is worth mentioning that New York restaurants have started adding automatic gratuity even though the number of people eating is far less than 6. Even with a group of three, gratuity of 20% may be automatically added both in restaurants and in 'pubs'. The automatic gratuity is also becoming common in areas that are highly tourist-oriented, such as the Grand Canyon.    It is important to always check your bill!

For buffet restaurants, tipping servers who clear multiple dishes and provide drink refills are recommended. Some persons may tip buffet servers $1 per diner, others as much as 5 percent of the total bill, depending upon the level of service provided.  Buffet servers may not take orders or bring out food, but they do work hard keeping your table clean of the empty plates after multiple trips to the buffet line. In addition to this, they often help to keep the buffet line stocked and clean, and they make coffee, brew tea, etc.  Remember that the minimum tip for any server should be $1 per person. Do not leave only 75 cents for a $5.00 buffet!  As always, if you feel you have not been well-served, adjust the gratuity down.  If a tip has been added to your bill beforehand because your party was 6 or more, but the server was inadequate or rude, inform the manager immediately before you pay your bill that you want the tip adjusted.

For bad or unacceptable service it is customary to  tip as low as 10% or even less for very egregious behavior by a server.  If service is bad enough to deserve only 10%, it is a good idea to let the manager know. Also, placing 2 pennies side by side on top of bills neatly placed on the table lets the server know that it is intentionally low because of bad service. If the server in some way offended you so that you do not wish to leave any tip at all, still leave the 2 pennies, so that they understand that you did not just forget to tip.

Counter service/fast food restaurants often have tip jars out, but you are not required to tip.  If the service is exemplary or unusual requests are made, then tips are appropriate.

Bartenders: $1 per drink, or 15-20% of the total bill. If you tip well and consistently at bars and pubs, you *might* receive a drink on the house, known sometimes as a "buyback" or "comp". This typically occurs after the 3rd drink you buy, however, is usually reserved for regular customers. Some bartenders will still use the "old school" signal of leaving an upside-down shot glass near your spot at the bar, especially if you are engaged in conversation or if the place is very noisy, but it's not that common anymore. Turn the shot glass over when you want the free drink. Even though the drink is free, the labor isn't. Don't forget to tip on the "buyback." Note that some bars do not allow this.

Other optional tipping situations common to travelers include:

  • Hotel housekeeping/maid service: $2-3 per night up to $5, more in high-end hotels.  Also more if there are more than 3 people in a room or suite. Leave the tip on your pillow or in a similar obvious place with a note that says thank you.  Leave the tip each day when you leave the room, rather than at the end of your stay, because your room might get cleaned by different people each day, depending on staff schedules. If you have additional items delivered to your room, such as extra pillows, hangers, luggage racks, tip the person who brings them $2 or $3.
  • Concierge: Tipping is never expected, but always appreciated.  The more difficult the request, the higher the tip. $5.00 and up per request is good.
  • In-suite dining waiter:  Always read the bill, if there is a tip included, it will be on the bill breakdown.  Ask the server.  The policy of having the gratuity included in the bill is not the norm anymore.  A service charge or convenience fee goes to the hotel, not the server.  If there is no gratuity added, tip the server 15% - 20%.
  • Bellman/Porter: $1-2 per bag. More if the bags are very heavy.
  • Taxi Driver: 10-15% of fare, based on service.
  • Hotel limo driver: For a free ride from the airport, $10 - $20
  • Drink Server in a casino or bar: $1-$2 per drink. Some tip $5 for the first drink to make sure the waitress "remembers" them and returns often...
  • Valet Parking Attendants: $2 - $5 (when picking up car).
  • Dealers at Table Games in the Casinos:   5% of bet amount at end of session, or occasional bet for dealer in amount of your normal wager-dealer can show you where to place bet.  You could announce " I have a $xx bet for the dealers, where do you want it?". The bet is usually placed in front of the player's bet. If you're concerned about having your bets rated for comps, place the additional bet on top of your own and tell the dealer that part of your bet is in play for the dealer and as long as your hands keep winning, keep toking the dealer with the winnings from that portion of the bet. The initial bet amount would be $1 - $5.
  • Slot machines host: $10-20 if they make a hand payout (over $1000).
  • Spa: For a massage or other treatment, 10% - 20%.  Ask if the tip has been included, some spas will include a gratuity on your final bill.  Most spas will provide you with an envelope to leave at the reception desk for the person who gave you your treatment.  Also, if you wish to leave a small gratuity for the spa attendant who showed you around the Spa and got you situated, it is well appreciated, $2 to $5.
  • Hairdresser/manicurist: 10% - 20%.
  • Showroom captains: $1-2 for the person who seats you, more if you asked for "special" seating - $20 for a requested booth or table, more for one up front. Unfortunately this is where the fine line between tipping and bribery meet...
  • Tour Guides: 15% - 20% + depending on quality (knowledge, friendliness, etc)

            ___________ 

The Americano-centric point of view is below on tipping:

Why are you expected to tip in the USA? 

In * some* states in the USA, waitstaff and bartenders in restaurants are paid below the minimum wage, because the employees are expected to make up the difference, so to speak, in tips. (However, please note that the employer is required by law to bring the hourly pay of the employee up to the USA Federal Minimum Wage if the server does not earn an adequate amount of tips.) This means that a server could earn far above minimum wage on a good night ($200 a night is not uncommon), or hardly break even on a slow night. Servers are expected to pay income tax on your tips -- they truly are part of their normal wages for the job they do, not just "extra" money for them.

Always leave tips in cash, handing them directly to the person you are tipping, whenever feasible  This makes certain that the right person is rewarded, and that the establishment itself cannot skim a portion of your tip by assessing the employee a percentage of what you tipped on the credit card.  Many places are legally able to do this now, so, unless you absolutely need to charge the tip for business reasons, a cash tip is almost always better for the tipee.  But the reason that servers prefer tips in cash is the fact that they can avoid declaring the income on their Tax Returns and avoid paying the Income tax and other payroll taxes on the amount. (Some do declare it, some don't). 

All 50 states have different minimum wage laws.  Some allow employers to pay less than the state's minimum wage to tipped staff, others do not. Federal employment compensation law requires that if employers pay less than minimum wage, tips must bring compensation up to the minimum wage or the employer must make up the difference.  Therefore, no server legally makes below the federal minimum wage in the U.S. regardless of the amount of tips received.

Many staff in Las Vegas are unionized, with benefits and high wages as well as getting tips.  These few are at the top of the industry and can make a six figure income.  Tips are expected regardless of what state you are in or what wages the staff are paid.  For better or for worse, tipping has become a part of most hospitality worker's pay.

Tipping in the USA is something you get the hang of after you do it a while. After a couple of days, you'll be able to gauge when you receive stellar service, or whether someone is "phoning it in." If you are mistreated anywhere, you should inform a manager.  Don't tip poor service - let someone know you were unhappy, even if you just leave a note to the server as to why there is no tip added to the bill.