When soup is served in a cup or round bowl with a plate under it, place your spoon on the underplate between sips and when you’re finished. The soup spoon doesn’t go back in smaller bowls because it’s too easy to accidentally knock it out of the bowl and send it flying. Also, wait staff have to remove it before they can pick up your bowl because it will fall out if they try to carry it with the spoon still inside the cup or bowl.