By restoring free “third places” where people just go to hang out and either bump into people they know or meet new people. The sorts of interactions you get in the common room in a dorm or a school cafeteria.
Locally, we have plenty of non-chain coffee shops, a good selection of small breweries/pubs, assorted gyms of all types and prices (CrossFit, Golds, etc), the local community center has assorted classes (dance, language, arts), and the community college has plenty of evening courses across most subject areas. Toss in MeetUps and Facebooks groups and there's plenty of chance to do things with social groups.
We need to promote density, walkability and time.
In America there is an idea that anyone who wants more that 4 hours to live outside of work is lazy or in some form selfish.
We do need to model university a little bit imo. Give me stuff to do that I can get to with fair ease, give people the time and energy to do it and everyone will be a lot more social
I live in the suburbs, but almost everything is within 2 miles... office, schools, and one cafe are walkable. Gym, another cafe, pub, and the town center (privately owned mixed-use complex) are 2-3 miles, so long walk, short bike, or 5 minutes in the car. I wish it was more walkable, but compared to most suburban areas, it's really good.
Contrasted my sister's house, on the other side of the county... nothing is within 3 miles or so. Basically a car ride to do anything, as there's no bike infrastructure for those things that are within 3 miles.
Think neighborhood parks and playgrounds. A dog run. The clubhouse or member center at a housing development. Houses of worship are still such a place for a lot of people. The streets where kids used to play and ride bikes but that we no longer let them out onto. Stoops in some urban neighborhoods (which in many have ceased to be a third place due to the cultural changes accompanying gentrification). On the other end of the social spectrum, gentlemen’s clubs.