Teaching the 'COME' command
Dogs enjoy exploring their environment naturally by sniffing all around the area, digging, turning things around and running away with little objects. A training session is best done when you keep your dog away from other distracting voices and people. A clear yard without any little objects is the best idea for such a purpose.
Be sure to take full advantage of any spontaneous behavior you see. For instance when you notice the dog coming at you, give a voice command along with a hand gesture to reinforce this behavior. Try to use a word and sign that you don't normally use during your teaching sessions.
Put the dog in a sitting position facing you. Reinforce the command of 'stay' as you move away. Use hand gestures and voice commands. Praise the dog if the behavior is correct. Do not reward the dog for an incorrect or partial response.
Repeat this as you continue stepping back several more steps. If the dog comes to you before he should, give the "sit-stay" command and try it again. If the dog doesn't want to come at all you may have to use a toy or a treat to encourage him a little bit.
For dogs that are sluggish students, or a little reluctant, leash and collar training may be necessary. Put your dog in the sit/stay position and begin to move back a short distance as you are playing out some excess on the leash. If your dog resists, give a soft tug that is pronounced while giving the verbal command along with the hand signal.
If the dog follows you too quickly, use a long lead and wrap it around a tree. Tugging the leash if the dog starts to get up early can stop it as you say stay. You can use the help of a friend, if there is no tree handy. But the dog is going to get confused about whom to obey. They focus best upon just one person.
One needs to be consistent as well as patient during a dog training session. Dogs do not understand the need for such commands like 'sit', 'stay', and 'come'. Do not speak harshly to your dog if he does not obey you at the first instance. This is a counterproductive measure. You need to establish your alpha status firmly by your body language, and readiness to wait for your dog to obey the given order. Physical leading and physical punishment is not such a helpful technique.
Many dogs rapidly show themselves to be happy to please and are very solicitous of praise following the correct behavior. Just be sure they're the ones 'coming', not you. If you have to, prove that you're the demanding one when it comes to their behavior.