1 Add soap to the wet cloth to wash your baby's body. 2  Wash the diaper area last. 3  Rinse your baby off with water and pat your baby dry. 4  Cup your hand under warm water and gently pour it over your baby's head to wet your baby's hair. Soap the washcloth (use a gentle, no-tears baby soap or wash) and clean your baby's body from top to bottom and front to back. 2  Make sure you clean inside all of the little folds. 3  Wash the diaper area last. 4  Fill a cup with water to wet baby's hair.