As the number of on-line classes and the demand for on-line education continues to sky-rocket, it is critical that course developers and university faculty have the skills to effectively design curricula, to develop engaging learning opportunities, and to create responsive courses that meet individual student needs. This paper details three essential elements, "Relationships, Rigor, and Responsiveness" (R3), in designing effective on-line courses: 1) building student and faculty relationships, 2) ensuring rigorous course content, and 3) developing a culture of responsiveness to students. An overview of these three essential elements are aligned to effective on-line course development, as well as course evaluation, with examples and guidance for incorporating these elements.