Punishment vs. withholding reward
A dog's mentality is very simple as it learns based upon "pleasant" and "unpleasant". When training a dog, we teach it that it is pleasant to display what the owner considers desirable behavior and unpleasant to display undesirable behavior. Therefore, it is imperative to understand when it is appropriate to reward, withhold reward, or punish. Every trainer has a different preference when it comes to the type of reward to give a dog. I prefer to use food when I'm looking for a little less excitement and more precision. I use a toy, such as a tug or ball, when I'm looking for exuberant enthusiasm and speed.
Knowing when to reward a dog for a behavior that is offered is a fundamental part of training. Some people use a clicker while others may use a verbal cue, such as saying "Good!", to indicate a correct behavior which is followed by the reward. The clicker or verbal cue serves as "marker" which signifies to the dog that the specific behavior it just performed is what got him the reward.
When a dog is learning a behavior, the handler's patience is going to be key in this teaching phase. If the dog is learning "Sit," gets mixed up, and does a beautiful "Down", the dog should not be punished. Instead, withholding reward should be used. In this situation, the dog is learning something new and should not be punished for something it does not truly understand. If the dog lays downs on the "Sit " command, I say something like "Nope" which is used to tell the dog that it offered a behavior trying to please me, but it was the wrong behavior. The "Nope" is what I call an "anti-marker" which means no reward is going to be given.
Punishment should only be used when a dog intentionally disobeys a command that it clearly understands or if the dog is trying to please itself in a negative way. For example, if my dog tries to fight another dog, I'm not going to use an anti-marker and withhold reward. I'm going to use a negative command followed by punishment in the form of a leash correction. When the dog realizes the mistake, and begins to please me by displaying appropriate behavior, I will reward it with a marker.