If the dog makes a mess in the house - slap YOURSELF. You didn't do your job, and that's in no way the dog's fault. You let him down. If you have to supervise him and not let him "wander off".  

The idea is to take advantage of a rule of dog behavior: a dog will not generally eliminate where it sleeps. Exceptions to this rule are:  Dogs that are in crates that are too large (so the dog can eliminate at one end and sleep at the other end).  Dogs that unfortunately have lived in small cages during critical phases of development and have had to learn to eliminate in the cage.  Dogs that have blankets or other soft, absorbent items in the crate with them.  Dogs that are left for too long in the crate and cannot hold it any longer.

If the crate is too big, you can partition the crate off with pegboard wired to the sides to make the crate the correct size, and move it back as your puppy grows. To house train a dog using a crate, establish a schedule where the dog is either outside or in its crate when it feels the need to eliminate.  Using a mild correction (saying "No" in a firm, even tone) when the dog eliminates inside and exuberant, wild praise when the dog eliminates outside will eventually teach the dog that it is better to go outside than in. Some owners correct more severely inside, but this is extremely detrimental to the character of puppies. To make the dog notice the difference between eliminating inside and outside, you must praise more outside rather than correcting more inside.  The crate is crucial because the dog will "hold it" while in the crate, so it is likely to have to eliminate when it is taken out. Since you know when your dog has to eliminate, you take it out and it eliminates immediately, and is praised immediately. Doing this consistently is ideal reinforcement for the behavior of going out to eliminate. In addition, the dog is always supervised in the house, so the dog is always corrected for eliminating indoors. This strengthens the inhibition against eliminating inside.

In general, consistency is MUCH more important than severe corrections when training a dog. Before a dog understands what you want, severe corrections are not useful and can be quite DETRIMENTAL. Crating allows the owner to have total control over the dog in order to achieve consistency. Hopefully, this will prevent the need (and the desire) to use more severe corrections. Housetraining is relatively simple with puppies. The most important thing to understand is that it takes time. Young puppies cannot wait to go to the bathroom. When they have to go, they have to go NOW. Therefore, until they are about four months old, you can only encourage good behavior and try to prevent bad behavior.

First rule of housetraining: puppies have to go to the bathroom immediately upon waking up.

Second rule of housetraining: puppies have to go to the bathroom immediately after eating.  With these two rules goes the indisputable fact that until a puppy is housetrained, you MUST confine them or watch them to prevent accidents.  This means that the puppy should have a place to sleep where it cannot get out. Understand that a puppy cannot go all night without eliminating, so when it cries in the night, you must get up and take it out and wait until it goes. Then enthusiastically praise it and put it back to bed. In the morning, take it out again and let it do its stuff and praise it. After it is fed and after it wakes up at any point, take it out to eliminate.  Make it aware that this is not play time, but understand that puppies get pretty excited about things like grass and snails and leaves and forget what they came outside to do! Use the same spot each time if you can, the smell will help the puppy remember what it is to do, especially after 12 weeks of age.

To make life easier for you later on, use a key phrase just when the puppy starts to eliminate. Try "hurry up," "do it," or some similar phrase (pick one and use it). The puppy will begin to eliminate on command, and this can be especially useful later, such as making sure the dog eliminates before a car ride or a walk in the park.   Don't let the puppy loose in the house unless it has just gone outside, and/or you are watching it extremely closely for signs that it has to go. The key to housetraining is preventing accidents. If no accidents occur (ha!), then the dog never learns it has an option other than going outside.