Some dogs are easier to train than other dogs when it comes to housetraining. As a rule of thumb, some of the smaller breeds can be more difficult. In general, never punish a dog for an accident. Instead, learn how to reward the behavior you want and you will find quicker success.
 
Know what to expect.
Below is a list of how long a dog can hold the need to “answer the call of nature” at different ages. If your dog is only three months old and you can't put the dog outside for four hours, you need to expect an accident. Dogs, by nature will learn to keep their sleeping area clean. For that reason, confinement of a dog during the housetraining process is a great help. Either crate train your dog or section off a part of your house with a doggy gait. As the dog matures, he or she can better understand that his den area includes the entire house; however, don't expect a young pup can grasp that idea.

Approximate Time Table Dog Can “Hold It”
Dog Age Time
2 months  2 hours
3 months 4 hours
4 months 5 hours
6 months 7 hours
7 months 8 hours

Know what causes exceptions to the rule above.
If your dog is more active, he or she will need to go more often than listed above.
If your dog is less active, such as when he or she is sleeping, the dog will be able to hold things longer.
If you have a smaller breed of dog, the dog may take until he or she is almost a year to achieve good bladder control.

Take advantage of when the dog need to answer the call to help teach the dog where you want him or her to do the dog's business.
Younger dogs typically need to go:
After exercise or playing
After they eat
After they wake up
If the dog hasn't gone in regard to the table above

To encourage a dog to do his or her business, go outside with the dog on a leash, walk the dog around until the dog answers the call, then reward with praise and a really nice treat.

Realize when you have an advanced housetraining problem.
Some dogs have issues beyond what the above training can solve. Those issues include:
The dog marks in the house
The dog eliminates after you leave the house (frustration elimination may be a version of separation anxiety)
The dog pees when you approach
The dog pees when you come home as a form or greeting.
If any of those problems are plaguing your dog, there is an entire chapter in the book Training the Hard to Train Dog to help you solve your problems.