I'm self-employed and I have a rented desk at the local WeWork coworking space. I go there when I feel like getting out of the house to get some work done.
Using the coworking space is a surprisingly good way to meet people. Obviously the guy locked in an office, headphones on, hammering out code should be left alone -- but there will be many people sitting in the common areas, chatting with their buddies. They might be drinking the free beer on tap. They probably have a startup, open source project, etc. that they're passionate about and would be happy to tell you about.
I co-own/run a co-working space and always enjoy opportunities to talk with the others here about our work and life outside of work. I've been in a shared/open office my entire working life and many of my friends have come through these environments.
I think consistently seeing each other daily for whatever period gives you a good chance to find common interests, incorporate social outings, etc.
Using the coworking space is a surprisingly good way to meet people. Obviously the guy locked in an office, headphones on, hammering out code should be left alone -- but there will be many people sitting in the common areas, chatting with their buddies. They might be drinking the free beer on tap. They probably have a startup, open source project, etc. that they're passionate about and would be happy to tell you about.