Traditionally, gratuities were considered -- hence, the word -- gratuitous.

"The original point of tipping was to say that I've had especially good service, and I want to acknowledge and reward that," said Mary Herczog, author of "Frommer's Las Vegas" and "Las Vegas For Dummies."

Forty years ago, notes Florozeen Gray, president of the Protocol Etiquette School of Nevada, the change left over from a transaction was accepted and appreciated.

However, as Gray noted, "in today's society, we set a standard on tipping." A specific percent or dollar amount is expected to be rendered after a specific service is provided -- as long as it's not provided poorly.

It's not surprising then that tip-takers have grown to take what should be considered gifts of appreciation for granted.

"Workers have been forced into this position, some of them, by the bottom-line stinkers, who are cheating their employees and expecting that their customers will make up for what is their responsibility, which is to pay their employees what they're worth," said Herczog.

In fact, since 1994 -- when the IRS instituted the Social Security tip credit -- servers have been paying taxes on their tips.

"And, as the employees had to report what their tips were, I'm sure the business owners saw that these minimum-wage people were making some good money," said Gail Sammons, chairwoman of the Hotel Management Department at the University of Nevada, Las Vegas.

Accordingly, the base salaries of the most heavily tipped jobs usually do not keep pace with the cost of living.

"A small gesture of a few dollars could have a great impact on the life of someone in the service industry," Gray said. "Plus, it is the right thing to do."

But how much do service providers deserve ... and do they always deserve something?

The Review-Journal surveyed five service-industry experts, seeking to gauge the proper gratuities for 24 commonly tipped Las Vegas services -- if they're performed well.

Remember to check if a service charge, normally 15 percent to 18 percent, is already included in your bill, and adjust your tip accordingly.

Gail Sammons

Chairwoman of the Hotel Management Department at the University of Nevada, Las Vegas

Waiter: 20 percent

Waiter for a comped meal: 25 percent

Cocktail server: 15 percent to 20 percent, $1 per drink if comped

Bartender: 15 percent to 20 percent

Sommelier: 10 percent

Restaurant maitre d': $10 for an upgrade

Cab driver: 15 percent to 20 percent

Food deliverer: 20 percent

Valet parker: $2 in, $2 to $5 out

Bellhop: $2 to $5 per bag, depending on weight

Concierge: 10 percent of the service

Maid: $5 per night

Room service: 20 percent

Washroom attendant: $1 to $2

Dealer: 10 percent if you're winning, $1-$2 if you're losing

Poker dealer: n/a

Slot jackpot: 10 percent

Skycap: $2 to $5 per bag, depending on bag weight

Airport overflow parking van driver: $2

Hairstylist: 20 percent

Shampoo person: $1

Manicurist: 20 percent to 25 percent

Massage therapist: 15 percent to 20 percent

Pool attendant: $1 to $2

Mary Herczog, author, "Frommer's Las Vegas" and "Las Vegas For Dummies"

Waiter: 15 percent

Waiter for a comped meal: 15 percent

Cocktail server: 15 percent

Bartender: 15 percent

Sommelier: Zero; they're just doing their jobs. I don't get the point of that.

Restaurant maitre d': Zero; unless you're trying to bribe them for a table, then it's $20

Cab driver: 15 percent

Food deliverer: $1 to $2

Valet parker: Zero in, $1 out

Bellhop: $1 per bag

Concierge: Zero

Maid: $2 per night

Room service: 15 percent

Washroom attendant: Loose change

Dealer: $1

Poker dealer: $1

Slot jackpot: Zero; to hell with that, that's mine

Skycap: $1 per bag

Airport overflow parking van driver: Zero

Hairstylist: 15 percent

Shampoo person: Zero

Manicurist: 15 percent

Massage therapist: Zero

Pool attendant: Zero

Florozeen Gray, president of the Protocol Etiquette School of Nevada

Waiter: 15 percent to 20 percent

Waiter for a comped meal: 15 percent to 20 percent

Cocktail server: 15 percent to 20 percent

Bartender: 15 percent to 20 percent

Sommelier: 15 percent to 20 percent

Restaurant maitre d': As much as $20

Cab driver: 15 percent; 20 percent if baggage is loaded and you're helped in and out of the taxi

Food deliverer: 10 percent

Valet parker: Zero in, $2 to $3 out

Bellhop: $1 per bag; $2 if bags are carried to your room

Concierge: $5 to $10

Maid: $1 to $10 per night, depending on how messy your room is

Washroom attendant: $1

Dealer: n/a

Poker dealer: n/a

Slot jackpot: n/a

Skycap: $1 per bag

Airport overflow parking van driver: $2 to $3

Hairstylist: 10 percent to 20 percent

Shampoo person: $5

Manicurist: 15 percent

Massage therapist: 20 percent

Pool attendant: Zero

Michael Politz, publisher, Food and Beverage Magazine

Waiter: 20 percent

Waiter for a comped meal: 20 percent to 30 percent

Cocktail server: 20 percent

Bartender: 20 percent

Sommelier: Zero; why tip them, they're on salary. And you're tipping the (sommelier) for their advice on wine that they're pushing for the restaurant to make more money on?

Restaurant maitre d': Usually, zero, but if people are in front of you and there's no other way to get in, maybe $20 a person.

Cab driver: Round up to the nearest $5.

Food deliverer: 10 percent to 20 percent

Valet parker: $2 to $3 in, $2 to $3 out. But $20 if the sign says "valet full." (Mr. Jackson always has a spot waiting for him.)

Bellhop: $5 per bag.

Concierge: Zero

Maid: $10 per night

Room service: 20 percent

Washroom attendant: $2, but that doesn't mean I don't hate it. You can't wash your hands without tipping someone a buck? There are times that I won't even go into the restroom.

Dealer: 10 percent of your winnings

Poker dealer: n/a. I play video poker. I never tip the machine.

Slot jackpot: $50 to $100

Skycap: $5 per bag

Airport overflow parking van driver: Zero

Hairstylist: $10 to $20

Shampoo person: $5

Manicurist: $5

Massage therapist: Zero, you just pay for the service

Pool attendant: $5

Rick Garman, writer for vegas4visitors.com and author of "Moon Handbooks Las Vegas" and the "Complete Idiot's Guide to Las Vegas"

Waiter: 15 percent

Waiter for a comped meal: 15 percent

Cocktail server: $1 per drink

Bartender: $1 per mixed drink, 50 cents for opening a bottle

Sommelier: 10 percent

Restaurant maitre d': Zero, unless you're attempting to get something out of it, then $20

Cab driver: 10 percent to 15 percent

Food deliverer: 15 percent

Valet parker: $1 in, $1 to $2 out

Bellhop: $1 to $2 per bag

Concierge: Zero, if the concierge is getting you something you could have gotten yourself. But if they're getting you something you couldn't get on your own through your contacts, 10 percent of the cost.

Maid: $3 to $5 per night, depending on how messy the room is

Room service: 15 percent

Washroom attendant: $1, that's one of my biggest pet peeves. I can get my own paper towels?

Dealer: The amount of a bet on a significant win, and $5 to $10 if you're having fun on shift change.

Poker dealer: n/a

Slot jackpot: $20 to each person you're dealing with.

Skycap: per bag $2 to $3

Bell transit overflow parking van driver: $2

Hairstylist: 10 percent

Shampoo person: 5 percent

Manicurist: 10 percent

Massage therapist: 10 percent

Pool attendant: $1 to $2