Antique furnishings can be ruined by wet glasses, candles or massage oil. That exquisite comforter will be yard-sale material if it gets a single coffee or wine stain on it. And remove the sham pillows before you go to bed. Innkeepers expect to wash sheets and pillow cases between guests, but coverlet and shams can only take a few washings before they're too faded. If you have an accident such as spilled wine or soiled sheets or overflowing commode, alert the innkeeper before the damage becomes permanent.
Innkeepers are aware that accidents happen and are discrete.
Leave your ball cap back in the room during breakfast. That shouldn't need to be said, but four out of five innkeepers speaking about etiquette complained of guests wearing ball caps at the breakfast table. The fifth said he wanted to, but didn't want to sound like a snob. On the bright side, it's perfectly OK to leave your bed mussed, leave your dishes at the table, ask directional questions you thing are stupid, kick your shoes off on the porch, stay out late, wear jeans and a T-shirt to breakfast or ask for an iron, hair dryer, soft drink or phone book. You should expect to be served.