Don't be a Dick. Spay and Neuter your Pets.

If none are spayed or neutered, a female dog, her mate, and their offspring can produce 67,000 dogs in 6 years.

Ban Backyard Breeders along with Puppy Mills.  It is downright depressing to know how many puppies and kittens are abandoned and unwanted everyday in North America.  

Responsible people do their best to adopt from shelters but there is no way to keep up with the steady supply of newly orphaned animals.

The statistics can be found on the web.  I don't want to make anyone feel sick reading about it.  Take my word for it that too many animals die because humans no longer want the responsibility of caring for a pet.