Read your script thoroughly and mark the sections where you would like to use the fog machine. Since fog takes time to dissipate, consider the effect the lingering fog will have on the surrounding scenes.
Decide how you want the fog to look. You can choose fog that hugs the ground or fog that floats in the air. When choosing, consider how easily the audience will be able to see the action on stage.
Order a fog machine based on the number and type of cues you have and the type of fog you want. Some fog machines feature options such as remote controls and timers that can help you in getting your cues right.
Design your lighting effects with the fog machine in mind. The fog bends and diffuses the light, allowing you to create beautiful effects with colored stage lights, strobe lights and black lights.
Practice using the fog machine several times before the performance. Take note of how long it takes the fog machine to create enough fog for the effect you want. Adjust your cues accordingly.