Effective training programs consider a range of factors to determine the types, timing, and content of interventions for trainees. However, the distinct characteristics of individuals' knowledge and capabilities as a function of their level of proficiency can be among the most difficult factors to identify and address. Instructional interventions would benefit from a scientifically-derived framework matching stages of practitioner proficiency to the most powerful instructional strategies given learner characteristics. In response to this need, our paper presents an adaptive training framework for system developers. The framework incorporates best practices from the learning sciences and demonstrates application of a developmental model to design low-cost, high-impact training tools. Specifically, we identified instructional design strategies that promote trainee attentional focus, create necessary schema in long term memory, and filter incoming information efficiently to maximize training impact. We integrated these general principles with a mastery model defining the knowledge, skills, and behaviors of Marine instructors as they develop across five distinct stages of practitioner proficiency, from novice to expert. The resulting structure served as a roadmap and guide for selecting stage-appropriate instructional strategies, design elements, content focus, delivery methods, and learning assessments throughout the development of a training program for Marine instructors. Finally, we organized the stage-specific guidance into a broadly-applicable, easy-to-use framework for training developers. The design principles are scientifically sound, generalizable across domains and audiences, and combined, create efficient, high-impact solutions.