At a formal affair, plates are removed by a professional staff. But as most informal meals are served without help, the hostess clears the plates, often with the help of a guest or two. At a family meal, members clear their own plates.
Leaving the dining room. To signal dinner is concluded, the hostess catches the eye of the host, lays her napkin on the table, and suggests that everyone go into another room for coffee and after-dinner drinks. The hostess rises from her chair.
When it's time to leave, rather than detain one's host with a lengthy good-bye, make the departure brief but cordial.