Review all schedules, objectives, contacts, etc with your photographer. Discuss where and how the photographs will be used. Do you need horizontals, verticals, medium or large format, how much color vs. black and white, need for night images, etc. If the photographer is new to the campus, give a mini tour pointing out buildings and places which need to be photographed. Discuss any specifics you may need from each shoot.
Group shots versus extreme close ups.
Even lighting versus the dramatic. After the first few sessions a strong working relationship should be in progress. Allow for flexibility. One of the great assets of working with an outside photographer is that they are seeing everything with a fresh outlook. Allow them to explore, investigate new approaches.