Exercise
Every single dog out there needs exercise. It doesn't matter if they are the size of a small horse, or small enough to fit in your pocket; without sufficient exercise a dog becomes bored, unhappy, and unhealthy.
On average, dogs need about two hours of good exercise every single day. There are several factors that will adjust that number up or down, such as age, size and the overall health of your dog. The type of exercise is also going to vary dependant upon your dog and his abilities, due to the above factors. Some types of dogs, such as herding dogs, will need almost double that amount. If you don't wear your stock dog out in the morning, you might come home to a destroyed living room at night.
Big dogs need big runs! Some of them, like the Great Dane, will be happy with two good runs a day, but others, like the German Shepherd and Beauceron, are going to need a lot more, in addition to regular walks. These dogs excel at dog sports and need to be "worked" in order to keep their minds and bodies in tune. Hounds that are bred for tracking game over long distances are not going to be happy with just an hour at the beginning and end of each day, either.
Small dogs like Chihuahuas and Miniature Poodles still need regular exercise, even though they can't do the rigorous, ground-pounding runs that their larger cousins can do. A brisk, half-hour walk three times a day will keep these small dogs from rounding out and becoming ball-shaped, while still other pint-sized pooches will want more. Small terriers, even though they may weigh only twenty pounds, have a lot of energy in that compact body. They are going to need the full hour of play twice every day.

