How servers know a guest finish meal in a fine dining restaurant?
Good etiquette is to put your fork and knife laying catacorner on the edge of your plate. However, many people don’t know that and don’t do it. But if you see it, that is a good sign. Also, most likely they will do a fold action with their napkin and probably put it by their plate. Some people even push their plate a bit further away from them to signal to others they have finished. Check for any of those signs. Just be observant…
