Definitive screening designs (DSDs) are a powerful new approach to screening that provide the investigator a way to learn about main effects, two-factor interactions (2FIs), and quadratic effects in a number of runs that is roughly twice the number of factors. Main effects are orthogonal to each other as well as to 2FIs and quadratic effects. However, 2FIs and quadratic effects are correlated though not confounded. Still, this correlation makes foolproof model selection difficult. This talk shows how to take advantage of the special structure of a DSD to get the most clear-cut results possible.