First, I avoid dog parks. There are no regulations on who can/not enter these areas, and bad experiences can happen in a flash. I encourage people to participate in puppy socials and play groups organized by professionals to help build dog-dog socialiability in puppies.
From about six to 16 weeks, puppies are absolute sponges. Even though your puppy may not be able to walk around due to not finishing their vaccinations, carry your dog around and expose them to as many new environments as possible. The more things they can absorb, the better! When out and about, always micromanage new experiences to try to keep everything as positive as possible. Carry treats so you can always reward them during new interactions.
“Carry treats so you can always reward them during new interactions.”
There are also many checklists online that recommend various things to expose the puppy to as a great reference for owners. Even with all the work a puppy can be, make sure to enjoy your puppy and enjoy watching them grow and learn! They grow up fast, and these moments are precious!