Consumers around the world often give voluntary sums of money (called tips) to service providers after those workers have served them. There are no good measures of how much is tipped worldwide, but total tips in the US food and beverage industry alone are estimated to exceed $45 billion a year. Thus, tips represent more than small change and their salience and importance have grown in recent years with the advent of digital tipping, which has expanded both the number and types of services asking for tips and the size of tips they are asking for. Academic psychologists and other scholars have studied this topic for 50 years, but that information is locked away in academic journals and writing that is not easily accessible to the general public. This book brings that work together, along with new previously unpublished analyses, in readable prose that shares what we have learned about the topic - including why people tip, who are the best and worst tippers, why we tip some occupations and not others, why tipping norms vary across countries, and what factors influence the size of tips consumers leave. The insights revealed will benefit consumers struggling to navigate the complex and evolving expectations placed on them, tipped workers seeking to increase their incomes, managers of tipped workers interested in improving employee morale and customer satisfaction, and academics interested in further advancing our understanding of this fascinating behavior.