Get one of those rubber toys you can put a treat inside of.
Introduce it to the dog. Place it increasing distances from the dog (a knowledge of sit and stay commands will help here).
Eventually you can throw the toy. The dog will bring it back for another treat!
Eventually, you can only put a treat in ⅓ of the time. Then, never. However, your dog will remember the joy it took in fetching the toy/bone/whatever!
Tip: do not leave the fetch item in the dog’s possession during non-fetch periods.