Yes, long walks are pleasant, and you will have years of them ahead of you. But taking slower, loose-lead walks is a better idea during rapid growth. Some dogs will try too hard to keep up and can stress their young bodies. Instead, start slow and short, then work up to longer distances. Check with your veterinarian and breeder before starting this sort of program.
Biking and running with your dog are terrific forms of exercise, but not until he is full-grown orthopedically, which would be eighteen to twenty-four months depending on the breed. (Medium breeds might be okay at a year; again, consult with your veterinarian). Grass and earth are easier on a growing dog than concrete, so let him exercise on natural surfaces whenever possible.
Know your breed! A brachiocephalic (short-nosed) breed such as the Bullmastiff, Pug, Boxer, or Lhasa Apso can become overheated quickly. Heat can kill these dogs. Toy breeds, as vivacious as they are, should not be biked. Never mind that it is hard for them to keep up, but even a minor accident could cause them major injury.