If you tip the maid for not cleaning your room, you should also make sure to stop by the valet desk with a $20 and apologize for not parking a car, drop $10 off at the business center as a thank you for them being ready to deliver incoming faxes you didn't receive, and give $50 to the concierge for not helping you get a reservation at that Michelin starred restaurant you didn't have time to visit on this trip.