Having myself and family members worked in housekeeping years ago (not in a motel/hotel but similar kind of situation), I've been on both ends of the tipping experience.
Most housekeepers prefer that you don't attempt to make the bed because they have to pull it apart anyway. They do appreciate all the disposable trash gathered into one bag or stack.
For towels, washcloths, and bath mats, either toss them into one pile in the tub or on the bathroom floor. The rule is, they are supposed to change out all bath linens, whether they think they were used or not. The default for the housekeeper is, assume the towels hanging up are used.
