lv4dogs gave some great advice! Our Murphy is almost two, and he sometimes chews on things--plants, CDs, catalogs, socks, etc. He is not crate-trained (never took to it), and we don't have a yard because we live in the city, so we just have to keep an eye on him. Whenever he chews on something "bad," we tell him NO very firmly and loudly, pull him away or give him a squirt from a water bottle (he doesn't like water much), and give him one of his toys. This seems to be working. He gets plenty of play time and walk time, and he LOVES a Kong stuffed with peanut butter or with Milk Bones. Rawhide sticks keep him busy, too.

Someone once told me that dogs aren't fully mature until age 3...so we're almost there!