The document outlines 8 principles of prototyping: know your audience and intent; plan a little and prototype the rest; set expectations; you can draw; it's a prototype not the Mona Lisa; get feedback early; iterate often; and have fun. The principles are meant to guide prototyping and provide tips such as planning enough to have a direction but leaving room for iteration, setting expectations that the prototype is not final, and getting feedback frequently to improve the prototype.