Try to bend the first piece dry. Try to bend a second piece after it has been soaked in cold water for a time. Try a third piece after it has been soaked in hot water, and a fourth piece after it has been steamed. You can make a steamer like either of the above. Be careful, as steam and hot water can inflict severe burns.
Some people say the steamer needs to have a great deal of water, and use a drum.
Try bending different materials, birch, spruce, willows and other natural materials after they have been steamed. Cut or split two identical pieces of wood. Soak one in very warm water, bend it, and let it dry. Steam the other piece for quite a while, and bend it and let it dry. Test both pieces.