Infants from birth to 6 months grow quickly, and parents can almost immediately start them on the path to healthy development. Newborns cry to communicate a need while infants at 6 months begin to imitate language. Parents can repeat the cooing sounds their baby makes to establish communication skills, according to Parents. They can help their babies understand cause and effect by placing their baby on his back within kicking distance of a rattle or shaker. Babies enjoy the sound that the rattle makes when their feet make contact with it. To develop strength and flexibility, babies from birth to 6 months should engage in parent-supervised tummy time.