This case study is designed to be a teaching guide for graduate and undergraduate students in behavioral science courses, as well as a resource for practitioners curious about this field. It is intended to help readers practice applying a behavioral diagnosis and design methodology to a real-world challenge: increasing attendance at an informational meeting about an earned income tax credit-like benefit for single working adults in New York City. The case study describes the context and the challenge, explains the behavioral diagnosis and design methodology, offers a framework for identifying behavioral barriers and solutions, and leads readers through three practical exercises. Following the exercises, the case study describes the interventions actually tested as part of the Behavioral Interventions to Advance Self-Sufficiency (BIAS) project and reports the results of those tests. The case study concludes with a set of questions for further discussion. The case study aims to teach readers how to: (1) analyze a problem using a behavioral science lens; (2) identify possible reasons the problem is occurring based on research from behavioral science; and (3) develop a behaviorally-informed solution to address the problem.