Training & Teaching a dog "heel"

The exercise of training and teaching a dog to heel is very useful when taking your dog on a walk especially in crowded places because it will teach the dog to always walk next to you.
After you have taught your dog the other basic obedience training commands, the dog will be ready to go out with you on walks. At the same time the dog is learning to follow you while on the leash, you can also teach him to walk besides you. This is something that dogs don't do alone and need to get taught to do. With patience and consistency your dog will learn to walk on your left, perfectly synchronized with your speed, in any street and environment. 
Put your dog on your left side and take the end of the leash in your right hand about half way down with your left hand. There should be no slack between your left hand and the dog's neck.
Give the command "Sit."
Now bring your hand with a treat in it to the front of your dog's nose. Say your dog's name and then the command "Heel."
Begin walking for a little distance with the food still in front of your dog's nose.
When coming to a stop, repeat your dog's name and the command "Heel" while raising the treat above your dog's head so that he sits.
Then, reward your dog if he obeyed all your commands.
Repeat as often as necessary until your dog is consistently and reliably walking beside you on a leash. Then try this in a new place with distractions.
Once your dog had learnt to obey even with distractions you can begin training him with the "Heel" command without the leash.
It is important to note that even if your dog learns "Heel" perfectly he still should be kept on a leash in public places. As much for his safety as others.