Infuriated diners write that restaurant reservations are a bad joke. Francis J. Seidner, for one, reported a long, sad saga of having to wait for his reserved table at Le Bagatelle, Two Continents, and twice in a row at Dominique's Restaurants have their own sad side of this story, though. Alexander's III tells of patrons, particularly out-of-town visitors, making double reservations. The Jockey Club claims that as many as twenty per cent of their reservation don't show up, which reduces the restaurant's revenue and the waiters' tips, and ultimately encourage overbooking. You will understand if you hear the gratitude when you call to cancel a reservation. Some restaurants try to minimize no-shows by taking patrons' telephone numbers. L'Auberge Chez Francois has set up an annoyingly elaborate system for taking reservations two weeks ahead and requiring patrons to reconfirm the day before - on a phone that must be second only to Metro Information for busy signals. Many restaurants are refusing to take reservations at all. Restaurant Association president John Faraclas reminds that the restaurant's responsibility is limited to holding a table for fifteen minutes, then trying to seat late-serving patrons as soon as possible. Some irritation could be avoided if staff taking reservations would double-check the reservation so clerical erros - wrong day, time - are minimized. Diners should recognize that their responsibility lies in canceling as soon as possible reservations they can't keep, or showing up on time. Bungled reservations are an inconvenience to the diner, but they are a matter of livelihood for the restaurant.