Poems need to be grounded in the earth, in real things. There is more suggested by a baby's hair in a brush than all the rapturous generalization about goldilocks. Have the students think of an article of clothing they found very uncomfortable or hated to wear. Then they could write about the unhappy occasion they had to wear it. This often causes emotional issues to surface.
Poetry is often about rebellion, challenging the status quo.
Students think of four words to describe food they adore or four words to describe food they can't abide. Then they write a poem about the food without saying what it is. This can be an amusing group exercise with students alternating lines. It can be funny and also gets them to effectively describe things in terms of sensory reaction. Ask the students ot remember a favourite person in terms of smell.