I'll never forget looking around on the metro in Washington, DC as a journalism intern in undergrad. A vast majority of the metro riders were buried in their Blackberries. Yes, this observation occurred a long time ago when Blackberries were still "a thing." Watching all these people engrossed in emails and texts I became amused. I christened the act of bowing the head down to one's hands the "Blackberry prayer." I've since learned a bit about when cell phone use is appropriate and when it's best put away.
When you're around others, especially in a one on one situation, leave the cell phone where it won't become a distraction; that includes riding in a car with your family. At restaurants cell phones don't belong on the table. If you're expecting an important phone call inform the other members at your party, excuse yourself and step outside the restaurant to take the call.
At work one's cell phone should have its own home. In a purse or a drawer. If someone needs you for an emergency you can be reached at work. And meetings? It's fairly easy to tell when someone is texting under that conference table. Think about it! When you're in the presence of others and you pull out a cell phone, what does your action say? Be engaged with those around you. We are conditioned to reach for the phone during a lull in the conversation. But we don't need it! Don't let a cell phone become a crutch.