Make up as many metaphors or similes as you can for a common object (light bulb, fireplug, telephone pole, flower petal, mailbox, show, cat's eye, leaf, stars, etc). Keep going until you run out of steam. Cross out all the obvious ones. Circle your most original or engaging. If you're feeling ambitious write a piece about the object using some of the metaphors, along with other exposition.
This prompt was taken from Writing Poems by Robert Wallace and Michelle Boisseau.