Don't use your phone in public
When we wear headphones in public, we're implicitly communicating that we don't want to be approached. We're denying ourselves and others real opportunities for connection.
The same is true when we spend our commute time from home to work glued to our smartphone. Aside from the occasional call or text, there are hardly any good reasons for doing so as the default.
These tools are useful and they can make our lives easier. The issue is when we use them in a mindless way. When they become the ones in charge.