Dog walking should please and enjoy both, you and your dog. However, it can put a strain on millions of dog owners.
It's very important to be good prepared technically. I mean a comfortable dog collar and lead. The lead should be of the length you need, convenient for you, it shouldn't chafe your hand, should lay comfortable in your hand. The dog collar should be chosen correctly too. 
How to train a dog to heel? First of all, it is important to realize that the dog walking begins from the very place in your house, where you decide to go for a walk. Exactly from this place and from this second your walk begins. And exactly from this second you have to take the initiative.
As a rule, dogs immediately understand what's going on and begins to show joy or commotion, or even run out by a door, because they know what will happen now.
It may seem to be a normal behaviour of a dog to be waiting for a walk. But, the dog behaviour, and your behaviour at this moment decide how the dog walk will go off in whole.
What does it mean? It means that your dog will lead you for a walk, not you will lead your dog. With all sequential consequences. The dog can like the command "Heel!", because many dogs think that the command "Heel!" means that now they with the owner will fly like an arrow from the bow into the street. They think if they will pull on the lead, the owner will shout for joy and even wave his/her hands! And it must mean the dog must pull harder! All the more so because the owner always says the command "Heel!" Roughly so many dogs think...
How to walk a dog?So, how to walk a dog? When the dog is anxious or runs to the door when you take the lead, firstly, you have to calm the pet. You may give the command "Sit!" and wait for dog to get its breath and to be calm. You may award the dog behaviour, when the pet is calm, can listen to you and be under control.
Put on the collar, fasten the lead. When the dog is excited, begins to pull and to run out by the door again, repeat the process from the very beginning.
Give the command "Heel!" and wait for the dog to be calm and to look at you. It's a sure sign that you can control the dog behaviour now.
Repeat the process again and again till you get the result. It's work not for one day and one walk. When the dog is adult, it takes much more time it to understand that YOU lead it for a walk, not it leads you. And such dog training needs more time.
Don't give up, if nothing comes out immediately. Nobody has results immediately. Just remember that every-day dog obedience training is 100% success.
Moreover, this process should be repeated even when the dog is adult, trained, obedient, but suddenly gets self-willed and obstinate. 
So, we fastened the lead, gave the command "Sit!", stepped up to the door and opened it. When the dog gets away, runs out by the door, bustles, you must repeat the process from the beginning till the dog get calm again. Don't forget to award the good behaviour of the pet, e. g., say "Good boy / girl!"
I know, it may seem to be waste of time, but you should understand that the dog must be calm when it goes into the street. Otherwise, it will be not the walk but torture...
After several times repeats the dog will take as a matter of course the fact it may not be excited and run by the owner.
Now, how to train the dog to walk on the lead in the street. When you are in the street the idea stays the same. Don't run after the lead, don't follow the dog when it relaxes its vigilance, gets nervous, pulls the lead. Slow down, give the command "Sit!" Praise the pet when it sits and gets calm. Give the command "Heel!" and begin your movement.
Attention: The worst you may do it's to pull the lead when the dog pulls forward. It's wrong.
Your task is to learn the dog that the command "Heel!" means if the lead is tight the dog must stand still!
That's why you MAY NOT follow the dog when the lead is tight, when both of you pulls on it. There's no sense, moreover, there's heaps of harm.
When you will sequentially, day after day do these rules you will see the dog will train to walk alongside of you. It's so easy - when you will stop your dog will stop too!!! 
The dog will stop pulling the lead because it will know that if it will pull the lead you will stop, and it will sit and will not go anywhere till it will be calm again.
We're glad you read our article. But remember: the dog will never go to heel on the lead after your reading of the article. Never! If you want it to happen, WORK! Train your dog every day. You don't need to train your dog at regular hours. Dog training is your relationships with your pet. Whatever you do, try to keep to the rules. And the most important - walk your dog with love!