How do I show my puppy that I am the leader of the "pack" without being harsh?
Your puppy's mother provides a good example of this. She will often demand the puppy lay down when he greets her. She does this by physically pushing the pup down with her paw, in effect she is requiring her pup show the proper respect. Needless to say, we do not necessarily want our pup to greet us on their belly but we do not want an undisciplined dog jumping up on us or mouthing our hand either. Require your puppy to meet you sitting in front of you and physically place him that way until he understands. Also you may want to give snacks and toss the ball but never forget to make a simple requirement first. Tell your puppy to "down" or "shake" prior to a snack or put him in a "sit stay" before throwing his ball. Remember not to nag but to only say commands once and then firmly but gently place him as you require. Simple lessons now will make his attitude toward training a joy, and he will accept your authority with out question.