Positive reinforcement is rewarding a desired behavior. In dog training a great tool to use is a clicker. A click makes a sound that can be used to mark a desired behavior. It's effective because the sound can be produced at the exact moment your dog gives you the desired behavior.
To start using the clicker you have to charge it. Charging is clicking and then rewarding with a treat or toy repeatedly so that they will associate the click with the treat. A dog that is not familiar with a clicker will never know what the sound is for, so you have to show them. By charging the clicker they will realize that the sound means that they will be rewarded. Positive reinforcement requires no physical force to get your dog to do what you want. The reward will make your dog want to repeat the behavior making it fun for the both of you.