I had not delt with puppies since I was a child until Sawyer and Sasha, (always adopted older rescue Collies). When Sawyer was a young pup he would play with some biting. If he bit a little to aggressive I would yelp like another young pup would do so he would learn to not bite as hard, worked. After 6 months I got Sasha so Sawyer was kept entertained by her.
Hard to beleive Sasha is now 2 years old and Sawyer will be 3 in December. Kind of weird to think with all the Collies I've owned through the years my current two have about the same life expectancy as me.