One tip I have is to use markers as you lay the trail, it is so easy to lose the start when you come back with the dog ! markers also help in advanced training to mark turns in the trail etc. I always leave either a deer foot or piece of skin for the pup to play with at he end of the trail, if this is not enough to keep it interested try leaving small pieces of meat or even dried dog food along the trail, with a larger portion of meat or dog food at the end.