Leerburg mentions the changing of direction.Having a longer lead than usual let the dog go forward loosen the lead then immediately do a 180 degree turn and keep walking.Dont call its name just do it abruptly and with conviction.Its the same principle as giving it a good correction.
Understanding the reason why a dog will obey a command and/or stop a behaviour is critical in being able to train a dog. The concept of the dogs mind basically goes something like this, if the dog receives a pleasant experience from a specific behaviour it is likely it will repeat the behaviour again. If a dog receives an unpleasant experience from a specific behaviour it is less likely he would repeat the behaviour. The dog is unable to rationalise to why something is pleasant or unpleasant he is only able to understand his experience of the specific behaviour
To teach the dog to obey our commands we must build an association between the action and the command or signal. The dog does not understand why he performs an action after a command all he associates are the consequences of obeying or disobeying it through past experiences
There are ONLY two reasons why a dog will not perform a command
# It is unable to do so
# It is unwilling to do so
The above sums up why some dogs walk properly and others dont.In fact it sums up all dog training