Depending on the size of the building, what I would probably do is:
One breaker at a time, connect the hot and the common together, then go to each outlet, light, etc... with a multimeter and do a simple continuity check. Might be labor intensive if this is a large building.

EDIT: I would also number each breaker, then whatever you find on that circuit, write that number on the light or outlet. That way you can make sure you didn't miss anything.