NY Bowhunter method is the way to teach the dog to come and have taught my puppy that way. Only thing is I don't give her a treat as they will come to expect it later on and then it's more training to ween them off of treats.

For so young a pup, I would just use the long leash. Call him while kneeling. If they ignore you, gently pull the leash to you. Make it fun. When he comes, make a praise himby saying excitely, "good boy!"

The same method is used to teach fetch. Get his favorite toy and throw it just far enough so that the pup can reach it and you can reach the leash. Then kneel down and say, "fetch". You can also use a long hallway with all the door closed then he has to come to you. But above all, MAKE IT FUN!