Are you crate training him? Are you limiting the amount of water you're giving him? Give him water every two hours. As soon as he gets done drinking, pick up the water. Take him outside just a few minutes after you give him water. Be sure you are taking him out the same door every time. Praise him after he goes potty outside. How long have you had him? Have you been working to try and housebreak him for awhile? If so, you'll need to give him a consequence when he has an accident inside.
On a side note, we hung a bell on our door. When our puppy wants to go out, she rings the bell!
at 8:00 PM on Nov. 2, 2008