Keep the pup up to date on all vaccines. Find places things to stimulate him while exposing him to the minimum of contagions. A tough task. Many schutzhund clubs are fairly safe, particularly on private grounds. Check with the local breeders and competitors about bringing your pup out to the club.
Parks are off-limits until all shots are completed.
Airports and piers may be a possibility. Scout these areas out for dog population before bringing your pup there. Allow your pup to visit people it meets, but do not allow people to fawn over or play with your puppy. A quick pet is more than enough. He needs to learn that the world people in it are nice, but he doesn't need to become a social butterfly.