I'd have to second the crate training thing! It works wonders. I house broke a puppy using the crate. Here's my two points to add to the other great suggestions:

-When leaving him overnight, don't just open the crate and let him come out and wander, attatch the leash and pick him up and plop him outside so he doesn't get the chance to pee on the floor. repeat whenever you have to crate him for excursions out of the house.

-Once he has done this a few times, you can work up to letting him out without picking him up in the mornings and leading him out on a leash.

- Make him go in the same spot outside. This really helped the dog I was potty training to "get idea". He learned that if he had to pee (in the morning or when I knew he's not done it in a bit), he should go there and then he would be allowed to explore. I also gave him a treat when he peed on that spot.

Hope this helps!