Every time he chews something he's not supposed to, "no" and give him an appropriate chew toy. Avoid wooden and rope-like toys because they feel too much like carpets, furniture and walls. Hard rubber toys like KONG products are best. Don't punish - redirect. If he's food-motivated, try a treat-dispensing puzzle toy. Give him raw bones (not cooked, and not the bones you can get from the pet store - these all splinter and break off in chunks that he can't digest, and they may cause a blockage). A KONG stuffed with peanut butter, especially frozen, is a great way to keep them occupied as well.
As far as exercise goes, take him swimming at lakes and beaches as much as possible and play lots of ball. Better yet, throw the ball into the water to wear him out physically and mentally. Play groups with other dogs his age will help as well. Give him a "job" like volunteering in an animal-assisted therapy class (he won't be the only hyper puppy!) or earning his Canine Good Citizen certificate. Avoid taking him on controlled runs. A pup his age, especially a large breed prone to joint issues, shouldn't be going on long runs. Try to keep him off had surfaces like pavement for now, too; grass is much easier on their joints. It's recommended to hold off on letting a GSD go on long runs until they're 18 months old.
This is just my advice. All my experience has been with GSD mixes (including a GSD/wolf mix, which was tough)... so you should take what I say with a grain of salt. I'm an experienced dog "guardian," but I haven't had a purebred GSD before, just rescues.
Last edited by Declan; 07-06-2014 at 10:58 PM.