This is an easy one. Extra service of any kind from housekeeping, a tip. No tip left if no extra service.
Hotel housekeeping is kind of funny – often I notice that there’s nothing askew in the room, it’s been cleaned properly and I have fresh towels, etc. So I make a mental note to leave a tip when I check out. Never fails that the next day I get no coffee, a dirty towel is left in the tub, that kind of careless housekeeping. Makes it easier to leave nice tips for extra service from anyone as I travel.
I don’t tip ANYONE who just does their job. It’s ridiculous. Any extra service equals a nice tip, always..