If you're someone who doesn't go out much, then suddenly decides it's time to be social, or
If you're new in town and don't know anyone, or
If you just figure it's time to meet some new people, or
If you've got nothing else to do on a given evening, or
If you happen to be shopping when your favorite craft store has their knit night...
You show up, sit down next to someone, and say "What are you working on?"
I've sporadically attended a few local knitting groups, including a brief appearance at tonight's meetup group. It's amazing how anyone from anywhere could just show up and ask "Can I join you?" and... they can!