You know, that’s what’s great about projections. There is no one ‘best way’ to utilize them. It’s one of the things I admire most about theatre directors. They are so creative and resourceful—they are finding incredibly original ways of using them. Some directors have set up a projector behind a screen on stage and project from the back, which produces a bright, vivid, unobstructed image. Others use built-in projectors in auditoriums or schools and project from the front. And just recently I’ve seen more directors exploring space outside of the stage—above, from the side, finding a way to get as many actors on stage as possible, but still using projection to represent the mood of the scene.
A general suggestion I would give is to treat your projection as another light element in your show. A very sophisticated light, but one that in some scenes may dominate, while other lights will need to be dialed down. It really depends on your lighting needs in each scene. The brighter your projector is, the better, and you’ll need a screen, whether it’s built, rented, or bought. And then using a basic laptop, put projections in a slideshow in Powerpoint or Keynote, and you’re off and running.