Many facilities offer discounts for long-term boarding. Go to a vet school. If you let your dog serve as a guinea pig for a vet in training, you may be rewarded with lower bills, without compromising the care your animal receives. Call animal control. Not to turn in your animal, but to ask about free or low-cost rabies shots and other vaccines.
Many counties subsidize the cost of certain vaccinations.
Stay out of the emergency room. There isn't much you can do if your dog waits until after office hours to become seriously ill or injured, but when it's not a true emergency, avoid emergency animal centers. You can't always control who you fall in love with, but if you can, try to steer your affections in the directions of a less expensive breed. Pedigreed dogs are subject to more than 300 genetically transmitted abnormalities. Go to the library and read about different breeds before you make up your mind about the kind of dog you want.