I let the guest know of this policy at the time they make the reservation and most of them will call ahead to let me know if they are going to miss their reservation. This is common courtesy. If you miss your starting time at the golf course, you are usually made to wait if not turned away all together. If you miss an appointment with your salonist you are charged for the service anyway. Not showing up for a reservation is along the same lines.
Time is money.
Next Post We used to make sure in a very friendly way when taking the reservation by phone that the customer understood we would hold the table for 15 minutes, and encouraged them to give us a call if they were going to be late. The first thing the host staff would do when they got in in the afternoon would be to call back and leave confirmations for that evening's ressies. It would clear the book the 24 hours before the event of the folks who weren't coming and left room for walk ins. I don't remember ever having to charge anybody. This scheme swings the balance of power back from the customer.