The role of the lighting designer within theatre is to work with the director, set designer, and costume designer, to create an overall 'look' for the show in response to the text, while keeping in mind issues of visibility, safety and cost. The lighting designer also works closely with the stage manager on show control programming.
We have modern, computer capable equipment for lighting design. From this station, the house manager can control all the lights in the building. There is a special emergency switch in the system that when thrown shuts down all the lights instantly. The house lights have emergency battery backup power to special lamps in the art deco sconces that provide illumination in any emergency.

From Wikipedia:Principles of Lighting
There are many general principles to lighting a stage, although to allow for artistic effect, no hard and fast rules can ever be applied. The principles of lighting include:

Qualities of lightingIn the pursuit of these principles, the four main qualities or properties of interest are: