Creating teacher-authored materials can be a challenging task for a variety of reasons. While relying on coursebooks to provide a ready-made structure to our classes, we often design our own materials to meet some of the specific needs and interests of our learners. Teachers usually approach the task of materials development through intuition and trial and error without a clear understanding of the principles of design that might help us in the creation of successful materials. This article outlines five research-based design principles that form the foundation of materials development and gives practical suggestions for how to put these into practice to produce materials that are aesthetically appealing, well scaffolded, authentic, affectively and cognitively engaging, and consistently revised and updated.