Simply turning them off and on may damage the equipment. Learn to operate the light panels and projectors. Many are configured for a particular type of platform. If you need an adapter, locate them and try them out in advance. If using an overhead projector, learn how to change the light bulb.
Many projectors have an emergency backup bulb.
Locate this and know how to use it. If using a digital projector that is also used as a video projector, learn how to switch from video to computer and back. Learn how to adjust the volume and focus on digital projectors. Bibliography Bernstein, Mark. A Promising Solution for Teaching Technology.