If possible, visit the hall before the event to see what type of lighting exists. Take some test shots.
You may want to put a filter on your flash based on the ambient light (florescent, etc.)to achieve correct white balance. Typically, in low light situations, the flash overpowers ambient light so a filter may not be needed. Remember that shutter speed controls the ambient light in flash photography.
High ceilings make bounce flash difficult so you'll need some type of diffuser on the flash to make it a larger light source. If you're doing staged shots use a tripod and possibly a reflector.
"Red is gray and yellow white, but we decide which is right ....and which is an illusion"