I have 2 labs and one of them is currently a 6 month old pup - so I can relate. At first he only chewed on his toys - recently he has started w/ teh shoes and which he didn't do before. What I do and it seems to work is when he has something he's not supposed to I give him a firm "NO" then put the item out of his reach...then I get one of his toys or rawhides and stick it in his mouth and he chews away at that. It seems to work, eventually they'll catch onto what they can and cannot chew...just takes time and patience!