When it comes to training with positive reinforcement, an important element of this is the reinforcer (the consequence of a behavior). In dog training (or training any other kind of animal), teachers often assume they know the value of the reinforcer they are using. But there is a possibility, they could be wrong.

An assumption about what is or is not positive reinforcement to your dog is just that…an assumption.
So often, new clients have treats that ‘they’ think their dog loves…until their dog gets a sniff and taste of my treats. And would much rather work for my treats.
I see many people praise their dog for good behavior by leaning and bending over to rub their dog on the head, but many dogs will lean or move away when this happens. In this case then, what was intended to be a reinforcer may actually be punishing the behavior instead. A negative consequence was added to the dog’s environment, which is positive punishment and can result in their dog doing the behavior less to avoid being rubbed on the head.
A dog may find ball chasing high value after rest time but may not be interested after a long hike in the woods. At that time, that a dog may value settling with a chew toy more.
Always keep in mind, when it comes to reinforcers, ONLY your learner gets to decide what is or is not reinforcing.
The only way you will know is by observing the impact of that consequence on the rate of the behavior. If you see more of the behavior, it is being reinforced. Otherwise, it is not. And sometimes, what you intend to be a reinforcer can actually be a punisher if you see less of the behavior because of the consequence.
Remember that the value of any reinforcer can and often does change depending on a lot of factors – the environment, the animal’s health, the animal’s activity level, genetics, as examples.
Practice being observant of your dog. Your dog will tell you what he does or does not value, what is or is not within his abilities at the time, how he feels.
And practice using that knowledge to help you be a better, more inspiring kind of teacher.
Oh…and of course, have fun!