Not every hotel you are going to stay in will have a bellman and concierge. Heck, some just have Frank, who makes $5.85/hour, asleep behind the desk. In this case, you needn’t worry — tipping is probably not expected. But if you’re staying in a place slightly more upscale, tipping is both customary and appreciated.
Because tipping is a way of rewarding good service, there is no way to say what is appropriate across the board. Tip at your own discretion, but keep in mind the following guidelines:
Valet: $1 – $2 (more in bad weather)
Shuttle Driver: $2
Doorman: $1 – $2 (for hailing a cab and/or helping with luggage)
Bellman: $1 – $2 per bag (when bags are brought up and down from your room)
Concierge: $2 – $20 (depending on the level of attention; for simple questions like directions, no tip is necessary)
Room Service: 15 percent of the bill or at least $2 (not required if gratuity is included)
Housekeeping: $2 – $5 per night (the messier you are, the higher the tip)
Coat Check: $1 – $2
More Tipping Tips:
CREDIT: http://www.independenttraveler.com/resources/article.cfm?AID=307&category=7

