In general, tip size should range from 15% to 20% of the bill’s total. If a waitperson covers the basics (is gracious, gets the food to the table, and is available to meet your needs), 15% is appropriate. When a waitperson provides more nuanced service, the gratuity should increase. Explaining menu additions, listening to dietary concerns, assisting with wine, and anticipating guests’ needs deserve reward. If my water is maintained during the course of the meal, service is rendered extraordinary (as I drink a lot of water). Tipping on exceptional service begins at 20%.