I found treats really effective when teaching my border collie to walk with me off lead. I would keep one (chicken or some meaty thing) in my hand and keep my hand down and out to the side I wanted her to walk on and take a few steps at a time then make her sit and she gets a treat. (she was 5 months and already knew sit when we got her)

You can do the same thing teaching the sit command by taking the treat just over his head slowly saying sit. As soon as bum hits the ground I give the treat and build up from there.

My dogs are tethered through the day on long leads (farm and no secure backyard) but a friend has a beagle pup who is very distructive and she was told to stuff wet dog food or raw meat into a kong (a type of ball what is meant to be undestructable that is hollow in the middle) stick in the freezer over night then when they go out ( or just whenever) to give the toy to the dog. The dog spends his eneergy trying to get the yummy smelling stuff out of the ball and stops him chewing on the furniture or her high heels because his attention is disracted - in theory could be a great idea.

Doggie school is also a great way to get out and socialise the dog so could be worth checking with your local vet where doggy kinder is.