For any preparedness plan to be effective it must be put to test or verified. Simulation methodology shows high potential for studying disaster and mass vaccination preparedness. Unlike physical drills, simulation models are less expensive, take less time to be conducted, and are well suited for testing alternative solutions. The decision makers can modify and analyze the model in order to test and evaluate numerous scenarios and operating parameters. In this paper, we offer a systematic approach that can be used with simulation analysis by practitioners to develop operating decisions for emergency preparedness in general and mass vaccination clinics in particular. An actual mass vaccination center in a county health department of a southern state is used to illustrate the proposed methodology.