Also- preparing a dog for this- I start with puppies- tug of war ( the pup always wins), holding on to a batton in a tug petting the dog- with encouragement but not a happy voice. The pup can not be noise sensitive- a high action pup, with tons of self confidence and seriously physically fit. Make sure the dogs hips are in great shape, hearts, elbows, etc.
The dog should not be afraid of other dogs- and really should come out of lines that are dedicated to this sport. The purpose of this sport is to have levelheaded dog- that is willing to read situations, act appropriate, independent minded- but totaly will follow instruction such as when to release and return to the handler.