If you want your dog to eventually use a dog door, ignore the door while you are working on basic housetraining. You have to accompany your dog out anyway, and you don't want to waste any time trying to get the dog through a dog door. The door comes into play later, once housetraining seems to be reliable.

Teaching a dog to understand the concept of a dog door when he constantly observes people going in and out of a normal door can be quite a challenge. You'll have to use a specific method. Have a family member on each side of the door, hold it open, and encourage the dog through. Send the dog back and forth several times, making a fun game out of it. Then hold the door only part-way open, and let the dog push it all the way open as you call him through. Gradually hold the door open less and less.

After you've played this game a few times, go to the door and encourage the dog to go through the door on his own. If it doesn't work at first, try standing on the other side of the door and urging him through with your voice. Keep working at it until he consistently gets it right.

Something to keep in mind when selecting a dog door is exactly what functions you'd like the door to have. For instance, there may be times when you don't want the dog to use the dog door, such as if the lawn is being chemically treated, the driveway is being repaved, or it's just too hot or cold for the dog to be outside. To be prepared for all possible situations, choose a model with a locking function that also provides a visual indication to the dog that the door can't be used when locked.