Not so very long ago, nobody had to worry much about public phone etiquette since the only phone anybody could use on a regular basis was located inside a private business or residence. Assuring privacy was usually as simple as merely closing a door.
Now, however, the world is a radically different place and issues of manners on the phone suddenly involve a lot of people besides the caller and the recipient involved. Some basic guidelines will help us all get along better since it seems the cell phone is most definitely here to stay.
First and foremost, callers out in public should use discretion about when they pull the phone out and start chatting away. Avoid doing so at times when others in the area have a valid expectation of peace and quiet, such as during a movie or another kind of performance. When it is appropriate to speak, show consideration by using a quiet tone of voice. It may be perfectly acceptable to talk on the phone in a restaurant, for example, but it is less than courteous to force other tables to hear all about your private business.
Cell phone etiquette goes beyond just not annoying strangers, however. Many people also annoy their friends and loved ones endlessly by thinking that their data plan is an opportunity to look up the answer to every question or issue. Settling an argument with a friend by asking Siri all the time is bound to mean fewer friendships in the long run.