Dogs in the hunting, working or herding groups - Labrador retrievers, Collies, Shepherds, Hounds require the most exercise. If your dog is in one of these groups and in good health, they should be getting at least 30 minutes of vigorous exercise (Frisbee, soccer, agility course, running) several times a week in addition to their daily dog walks.

For other breeds, pay attention to signs to determine how much exercise is enough. If they're still walking at full speed after 20 minutes, add another 15 minutes. Observing your dog's behavior should give you clues to when they're well-exercised.

Additional Tips:

• Limit your dog's outdoor activity in extreme weather, especially temperatures higher than 85 degrees.
• Older dogs, younger dogs, and dark-haired dogs are more sensitive to heat and should be walked morning or early evening to avoid heat exhaustion.
• Protect your dog's paws in cold weather. In winter avoid salted paths which can cause chemical burns on their foot pads. Protect your dog's paws on hot pavement, too. If it's hot on your bare feet assume it's going to be hot on your dog's pads as well. 
• RUNNING your dog remember - they are not wearing shoes (like you are) to protect their pads. Not all dogs like to run, or should be forced to run especially miles and miles, their pads can wear down and become raw without you knowing. Pads should regularly be checked if you run your dog. Consult with a veterinarian about the health of your dog before running him (DO NOT assume running a dog is good for him). Smaller dogs with little short legs should not be forced to keep up with a human running gate or larger dogs.  Running is NOT RECOMMENDED for small dogs, dogs with hip issues, heart issues, foot & pad problems, breathing issues, or by nature over-heat easily.    
• On long walks, don't forget to bring water for your dog if it is hot or they over-heat easily.
• Toy and Small Breeds need outside exercise and daily walks. Pugs for example are prone to obesity, so they require exercise to maintain a healthy weight.
• Always remember a healthy dog is a happy dog just like we human's but they require YOU to take care of them, they cannot take care of themselves. Be loving, intuitive and compassionate to your fur-baby.