Imagine your puppy running out the front door. You call him, waving a treat. But he'd rather chase a squirrel into the road than come back to munch on a treat. In addition to the obvious danger of Puppy getting hit by a car, he learns that he doesn't have to listen to you. He learns that he's in charge of what he decides to do and what he decides not to do.
Any area that the pup has access to must be kept clear and clean. Put out of puppy's reach anything you don't want him to chew or destroy. Do not allow your puppy to have unsupervised access to 'unchewables.' Do not chase the puppy in an attempt to take something away. Instead provide puppy with her own toys and teach her how to play with them exclusively.