Much of the existing group model-building literature focuses on approaches to defining model boundary and conceptualizing overall model structure including the creation of a backbone stock-and-flow structure as well as mapping key feedback structures into the model. Detailed formulation and parameter estimates are often left to back room techniques. This paper reports on the use of three scripts designed to engage groups in tasks related to model parameterization. The paper describes the context of the study—a group model building session hosted by the Ohio State University and focusing on infant mortality in the state of Ohio—and then proceeds to lay out the agenda for the two-day group modeling project. We discuss in detail how three scripts were used and also present a summary of the data that was collected to parameterize the final model. The paper sketches how that data has been used to support the rapid prototyping of the first phase of a running simulation model.