Predator animals have a natural instinct to chase.
Dogs are natural predators.
They will run after things or people.
Of course this is inappropriate behavior for a house pet.
Begin training your dog as early as you can.
When the dog is smaller, he is less of a threat to others and easier to control.
This especially is true with breeds that can grow very big or for those breeds that are very aggressive by nature.
Joggers or anyone else will be very scared when a dog is chasing them.
Some breeds are easier to train than others.
Those dogs that have been raised for hunters or herders might have much more of an instinct to chase than other dogs.
Regardless of his breed, do not let the dog outside without the leash until he no longer chases.
Let the dog be trained in an area that is closed and does not have others around.
The dog will learn how you want him to behave in this closed safe area.
Go over and over the proper behavior in this setting, letting him concentrate on you.
The place to do this is in your home.
Put the leash and collar on the dog and then show him a ball.
The animal should not touch the ball.
Push the ball to the other end of the room and state "off" to tell the animal not to go after it.
Pull the chain if your pet decides to go after the ball.
The dog should not be allowed to touch the ball.
Keep doing this until the dog understands what "off" means.
Give him a treat when he does not go after the ball.
Do this technique in another room as well after it is successful in one room.
Do this in several rooms.
After the dog understands the command, try this without the leash in a safe area still.