Developers who use the systems approach to training begin developing a lesson by identifying the skills and knowledge to be learned and the kinds of learning experiences required. The next step is to develop instructional segments. These segments include all instructor and trainee activities required to master the skill. Learning segments include the following components: presentation, explanation/demonstration, transitional practice (including cues and feedback), criterion practice (plus additional feedback), and a criterion test. Most of the learning takes place during active practice. Demonstrating and cuing are used to achieve error-free learning. The progression of the sequence is logical, with the criterion test forming the basis for student goals. (This module uses materials that might be included in a learning segment for nuclear power plant operators to illustrate the workings of the learning segment model. Step-by-step procedures for developing effective simulated practice are provided, including guidelines on scaling down practice and altering inputs, actions, and standards.) (MN)