depends what the dog is going to be working and also the breed of dog for a lamp dog lets say a collie x id start mine around 12 month old but only if the basic training i.e jumping,retriveing is all up to scrach.the key is takeing your time and getting to no your dog some breeds mature quicker than others if you now your dog then you will no the right time to enter it.time and patients is wots needed.some dogs will make the grade and others wont BUT YOU ONLY GET OUT WHAT YOU PUT IN. thats my opinion anyway A.T.B