I have brought my Model S to a few "Cars and Coffee" events, and to one or two other car shows. I have a tri-fold display panel that stands in my frunk with basic information about the car, and there have been just enough interested attendees to usually keep a steady stream of conversations going.
One thing I do is to allow people in my car. Including kids. The leather upholstery is tough, I am not afraid of damage, and have had none. That promotes conversation, especially when someone can sit in the front and see the big screen. When they ask about charging (which is topic #1), if they are patient I show them how the navigation system finds charging locations for them, and sometimes even have it plot a trip to show how that works.
Just don't park next to a Model X -- they get all the attention with the falcon wing doors!
Mostly, though, I attend EV-specific events, where we offer folks the chance to ride or drive. Those are a mixed bag. Their success depends heavily on the venue and why people are there. We have had some good experiences in library parking lots and shopping centers, but it does not always work well and the EV owners mostly end up talking with each other.