
There are many ways i have tried with dogs and one of them has worked.
1) is to turn direction quickly without a command and pul the dog into heel, they will soon learn to walk by you and watch you every move.
2) is to stop/walk backward and tell the dog to heel and then walk on again. do this everytime he pulls.
3) go out and buy a halti/gentle leader and use this on him, make sure it is the right size etc or it will not work.
Rox