This is an excerpt from an outstanding article over at Travel and Leisure Magazine on tipping. Traditional ways of tipping the staff have changed over the last couple of decades, and many travelers do not understand the what is expected of them in hotels.

Luxury hotel chains generally charge a service fee that ranges from 10 to 15 percent of the cost of your stay and covers housekeeping, the concierge, and other small services, such as having a newspaper delivered to your door daily. However, what it includes varies from property to property, so check with the receptionist. Most luxury hotels in China, Japan, and Singapore add a 10 percent service charge to the bill and say that additional tipping is not necessary. At Shangri-La Hotels, the 10 percent service charge is based on the traditional European tronc system, where fees are distributed not only among staff members who interact with guests, but also to dishwashers, laundry staff, and other employees.

 Ironically, European service fees are less uniform, ranging from nothing (at some small, privately run hotels) to up to 18 percent in Italy, where the Italian Government Tourist Board recommends additional cash tips for housekeeping (€ .75 a day), doormen who hail cabs (€ .25), concierges (€ 1), room service waiters (€ .50 minimum), and valets (€ .50). But this is not always the case. At the Hotel de Russie in Rome, for instance, there’s no service fee. In Turkey, though there’s likely to be a 15 percent service charge, it’s de rigueur to tip staff members on top of that, preferably in U.S. dollars.

Concierge By and large, say hotel general managers, it’s not necessary to tip a concierge unless he or she has done something extraordinary, such as secured tickets to a sold-out theater performance, chartered a boat, or retrieved lost baggage from your airline. In such cases, tip $10 to $50.
Porters Unless a hotel discourages tipping (as do some Caribbean all-inclusive resorts) or makes it clear that tips are not expected, you should give a porter a dollar or two per bag, regardless of whether or not your hotel has a service charge.
Housekeeping If your hotel adds service to your bill, check with reception to make sure housekeeping is covered. If it is, there’s no need to give an additional tip—unless the housekeeper does something special, like setting up a roll-away bed. However, if you’re staying at a small, privately run resort (or any hotel that does not have a service charge), you should tip anywhere from $1 to $3 a day. In Asia, while it’s perfectly acceptable to leave $1 to $3 per day in the room, guests are not expected to. (At ryokan, the tradition of placing a few yen in a decorative envelope is still widely practiced.) Tips are also not expected in Israel, Morocco, Egypt, Kenya, Dubai, Saudi Arabia, or South Africa.
Room Service and Valets In general, $1 to $3 is sufficient for room service delivery; valets should get between $1 and $5 for delivering your pressed clothes. Many hotels automatically include a charge of 10 to 18 percent on room service bills. However, as Ed Donaldson, a vice president of marketing at Small Luxury Hotels of the World, points out, “If you want great service and extra attention, it always pays to tip the delivery person, regardless of whether or not service is already included.”

Tipping Points | Travel + Leisure.