Once my dog had three sets of shots in, I started taking him to a local doggy daycare for a few hours once a week. It's a small private business and they are great and really work and get to know each dog individually. I purposely didn't ask about vaccines when I went the first time to see if she would ask me (kind of a test!). She was very strict about it and looked at each and every vaccine on my records to make sure they were up to date so I felt comfortable assuming the other dogs there are fully vaccinated too.
In the meantime, our new pup goes everywhere in the car that we do...ie - dropping off kids at school, drive-thrus, etc. and we have walked him outside in our neighborhood in the middle of the street (as opposed to sidewalks where other dogs obviously walk and do their business). Sometimes we literally just sit in our driveway together while I give him treats so he can hear other dogs. And our neighbor has a wonderful 7 year old fully vaccinated Australian Shepherd that is a very balanced dog and has played wonderfully with our new pup (to teach him the "doggie" rules). He has been great and I was so proud when my dog sat nicely while neighbor dog did the "sniff" test on their first visit.
I have taken my dog to pet stores for smells and seeing other dogs (no interaction), but I put a towel down in the cart and he rides in their and I carry him into the store...very careful!