By construction, optical (and near-infrared) interferometers typicallyhave resolutions designed to resolve stellar and circumstellarfeatures. Therefore gaging the point-source response of theinterferometer in its operating environment is critical to thescientific interpretation of data from these devices. This istypically performed with observations of calibration sources that aremodeled to be simple and quasi-unresolved by the interferometer.Herein I will discuss the goals and strategies for and issues with theselection of objects to serve as calibration sources for opticalinterferometry visibility measurements.