At the hotel
Before you arrive at a nicer hotel or resort, inquire as to whether gratuities are included in the price of the room. Some hotels are now charging a daily fee that covers all tipping for hotel services. If there is not a daily fee, these rates are appropriate:
Valet or parking attendant - $1-3 is appropriate for parking or returning the car. It is not necessary to tip for parking, but always for returning the car.
Doorman - If he hails you a cab, $1-2. If he helps you with your bags in or out of the car, $0.50-1 a bag. Use $1-2 per bag if he carries them all the way to the room. If he just opens the door, nothing. If he is exceptionally helpful with directions or restaurant recommendations, same as concierge.
Bellman - When he helps you with your bags, tip $1-2 per bag. Give him the tip when he shows you your room. If he just carries the bags to the front desk and then disappears, save it for the person who carries the bags to your room. Upon checkout, tip a bellman who helps with your bags. Tip more for additional services.
Concierge - $5-10 for help with hard-to-get dinner reservations or theater tickets. Tipping is optional for just plain advice. Tipping can be done at the end of the trip or at the time of service, just keep is straight so that you are fair.
Room Service - If gratuity is included, add nothing or $1. Otherwise add 15-20% to the total charge.
Delivery of special items - If you request extra pillows or an iron, tip $1 per item received, minimum $2.
Maid service - $1-5 per day typically, up to $10 per day depending upon how much mess you make. Tip daily because there might be a different maid each day. Leave the tip on your pillow. Err on the side of being generous, and tip on the last day also.
Swimming pool or gym attendant - Nothing, unless you require special services such as extra seating or inflating pool toys; then it is $2-5. If you want the same deck chairs every day, then tip $2-3 per chair beginning the first day.
Hotel maintenance staff - Nothing to replace a light bulb, fix the air conditioning, etc.