We asked etiquette expert and advice columnist Mary Mitchell for guidance in the following scenarios. Then we asked hotel workers what travelers really tip.

Q: Within five minutes of checking into a five-star hotel, you can encounter several service people, from the valet parker, to the desk person who escorts you to your room, to the bellman who delivers your bags, to the room service employee who brings complimentary tea. Whom should you tip?

Mitchell: Reward those who do the most physical labor. I wouldn't tip a doorman who just opens the door, but if he later hails a cab, I'd give him $1 to $5. If he helps with bags, in general give $1 a bag. The bellman: $1 to $3, depending on the number of bags. And the person delivering the tea: $1 or $2. I tip the valet parking person $5 when I pick up the car.

Mike Wente, guest services director at the Regal Biltmore Hotel in Los Angeles: If the doorman takes the bags out of the car, greets you with a smile and makes a nice first impression, give him $2 to $3. After check-in, our bellmen walk side by side with the guest pointing out hotel facilities. They take the bags and give an orientation of the room. Appropriate tip: $3 to $4 - though I've seen $10 to $20, and I've seen $1. Valet parkers usually get $1 each time the guest gets the car.

Q: Is it customary to tip the shuttle drivers who take you from the airport to the rental-car lot or hotel?

Mitchell: Yes. I tip $2.

Blair Sarkiss, shuttle driver for the Sofitel Hotel Chicago: Yes. Especially if we take your bags on and off; $1 to $2 is typical.

Q: Should hotel maids be tipped daily or at the end of the visit? And how much?

Mitchell:  It's such an important job, but maids usually get stiffed. The amount depends on where I am ($2 to $3 a night in a Holiday Inn in Missouri, for example; $5 a night in a city). Leave it daily so the person cleaning is the person who gets it.

Juanita Edwards, room attendant at the Sheraton Atlanta Hotel: Women are more likely to tip than men and Asians tip more than Americans or Europeans. But out of 18 rooms I'm responsible for, I'll find a tip in maybe three - anywhere from $3 to $5 a day.

Q: What is the correct amount to tip a hotel concierge?

Mitchell: For services like making dinner reservations, $5; $10 or more for special favors.

Sara-Ann Kasner, president of the National Concierge Association: Anywhere between $5 and $20, depending on the service, and more if they make miracles happen.

Q: When staying on a hotel club floor, where breakfast, snacks and drinks are set out throughout the day, should you tip the employees who clear the tables and maintain order?

Mitchell: You don't have to tip unless someone does a special duty. But if you're going back to the place, I'd invest $2 to $5.

Shawna Smith, club concierge, Four Seasons Resort Maui at Wailea: Guests don't typically tip, unless they're repeat guests or have developed a relationship with the staff, in which case, they tip at the end of their stay.

Q: Is it necessary to tip at a serve-yourself buffet?

Mitchell: Yes. The waiters really are performing a lot of service for you. It just looks different. Leave 15% to 20% on your table.

Chris Gwin, director of outlets at the Crowne Plaza Ravinia in Atlanta: People generally do tip 15% to 20% if the server is there to greet them, brings water and is generally attentive.

Q: When a service charge is added to a room service bill, should the waiter still be tipped?

Mitchell: A service charge is a tip, though you might come across with an extra $1 or $2 if the person is particularly pleasant.

Gwin: 80% to 85% of customers do not double tip, though business travelers on expense accounts are more likely to than vacationers.