The first 16 weeks of a puppy's life are the most critical for socialization. During this time dogs are more accepting of new experiences and environments. An adult dog's behavior is a result of both their experiences and their genetics. Puppydom is a time to nurture good experiences in order to prevent behaviour in the future.
A fun way to do this is with puppy socialization bingo!
Remember while playing the game:
Exposure alone is not socialization
Your dog determines if an interaction or experience was positive or negative. Not you or anyone else.
Never force your dog into an interaction...let them come to when they are ready.
Choose your puppies playmates, and experiences wisely.