One of the first procedures that you're going to want your dog to understand is where and when to go to the toilet.
As with most of the training you'll be undertaking, the key feature of toilet training is consistency. Always take him outside within 15-20 minutes of feeding so that he can understand the routine. In this case however, it is not just the dog that needs to be trained.
You also have to learn when he is telling you he must go outside. Look for telltale signs such as whining, circling and digging. If you think they need the loo take them outside immediately and reward them if they go. This positive reinforcement will let him know that you're beginning to understand each other.
One thing that is really important to remember whilst training is not to punish your dog if you don't catch him in the act. He simply will not make any connection between your current action and his previous one. If you catch him mid-stream, say 'NO' sharply, then pick him up and take him outside (picking him up should stop the flow!) then once he's completed outside make sure to offer a treat.