Agreed with most on here. However, housekeeping is always the one that gets me...If I stay somewhere for a few days especially, i am more likely to leave a tip than if it's just a couple of days. Especially if they do things like turn down service or leaving the weather report for you. Those are nice. As said, by some others, if the room is particularly tidy, you probably don't need to. But if you have trash everywhere, or leave a huge mess, then you probably should think about it. Especially if you are at the same hotel over and over again for work. This way, the staff may come to appreciate you and do a few extra things.

I used to work in a cheaper hotel, and we had several groups of guys who came in each week to do various different jobs in the area. One of the rooms had a guy that tipped the housekeepers. They always made sure his room had the newest and softest towels (some of them were pretty rough...but it was a cheap hotel) and if any of them had brought a cake or other dessert from home, they would always leave a piece for him! I know they did other things for him too but I can't recall them anymore. Point is, if you're there on a regular basis, get to know the staff and treat them good. They will return the favor.