In competition obedience training, “heel” means the dog is walking on your left side with his head even with your knee while you hold the leash loosely. Puppy training can be a little more relaxed with the goal being that they walk politely on a loose leash without pulling. Some trainers prefer to say “let’s go” or “forward” instead of “heel” when they train this easy way of walking together.
Keep your training sessions short, consistent and always have fun. The key to shaping your puppy's behavior is to start out with very easy commands, continue to build on these successes and apply heaps of repetition. Base your puppy training sessions around trust and mutual respect rather than old school methods based on punishment, avoidance and harsh corrections. In this environment you will find that your puppy loves his training sessions and his confidence will grow with each and every session.
Imagine your puppy running out the front door. You call him, waving a treat. But he'd rather chase a squirrel into the road than come back to munch on a treat. In addition to the obvious danger of Puppy getting hit by a car, he learns that he doesn't have to listen to you. He learns that he's in charge of what he decides to do and what he decides not to do.