How do you decide where to hold fairs and who will host?

At the end of the 2007 season we surveyed representatives of graduate schools who came to one or more fairs in 2007. We asked them to tell us how likely they were to attend events in a long list of cities. The cities with the highest ratings won, and then we looked for hosts. When a city had more than one possible host, we visited the school, looked at the event space, and made a decision based on many factors such as location, accessibility by public transportation, capacity, available break out space, and date availability.