This paper provides an in-depth view of computer based tutoring/coaching systems and (1) the philosophy behind them, (2) the kinds of diagnostic modeling strategies required to infer a student's shortcomings from observing his behavior, and (3) the range of explicit tutorial strategies needed for directing the tutor to say the right thing at the right time. Examples of these issues were drawn for a computer based system for a simple game--How the West Was Won. The intention was to make explicit the vast amounts of tutorial knowledge required to construct a coaching system that is robust, friendly, and intelligent enough to survive in home or classroom use. (Author/JEG)