Creating effective prototypes of game designs, user interfaces, and technologies requires a unique set of skills and knowledge, somewhat distinct from the skills used in making a game. This lecture discusses creating these various types of prototypes from an advanced and in-depth perspective. The talk goes through a number of important questions and topics that should be addressed before, during, and after the prototype is created, including metrics for judging the effectiveness of prototypes, how to decide the focus of a prototype, how to design, start, and build the prototype, both from a content and a code standpoint, and how to iterate the prototype via testing and integrating feedback. Various approaches to these issues are compared and contrasted, with the end goal of teaching attendees how to create successful and high quality prototypes.