Light & Energy
Light kindles attention, invites the eye into an image and shows the way through it.
It provides the choreography that dances the eye through the picture, marks the tempo at which things are revealed. And sometimes light can be the subject, what the whole picture is about.
So in this exercise, take your camera out into the world, look around, and make 100 pictures in which light itself is the main thing that is happening, the principal subject, perhaps even the only subject. While you're doing it be as thoughtless, and uncritical as you can be. Don't stop to ask yourself if this is what you're after. Just shoot and shoot and shoot.
When you're done set the work aside for a while—a few hours, a day. Then get it out and look at as though someone had handed you their work and asked you to find the good pictures.
But don't look for what you might think of as good pictures. Look for the pictures that are alive. If you concentrated on alive, good will take care of itself.