This document discusses prototyping as both an artifact and a process. It provides reasons for prototyping such as working through designs, communicating concepts, testing with customers, and gauging feasibility. Eight guiding principles of prototyping are outlined, including knowing your audience and setting expectations. Paper prototyping techniques like handlebars and accordion folds are presented. Benefits of prototyping in Fireworks and HTML are also summarized. The document promotes prototyping early to reduce risk.