Cell phones pose a unique issue.  You can have them with you no matter where you go. Especially with the small ear pieces available, you may have seen those people walking through the airport who look like they are talking to themselves.  It is pretty amusing until you have someone shouting into the phone three feet away from you, oblivious to the fact that others are even in the area.

All of the phone etiquette rules apply when talking on the cell phone, but because cell phones are so portable, you also need to be aware of where you are having your phone conversation.

People tend to speak more loudly when they are talking on the phone.  I noticed this myself when I was in the grocery store and had a question about the type of plates to buy.  I called home to ask and noticed how loud I was.

In theaters or places where there is a speaker, they generally ask that cell phones be turned off.  If you are at a play, movie, wedding, funeral, church, restaurant, or any type of presentation, turn off your phone or set it on vibrate.  If it is a call you absolutely must take, go to the lobby or another remote location so as not to disturb those around you.

Outside, away from others is the best location to take or make a cell phone call.  Aside from being considerate of others, you are also protecting your own privacy by keeping your phone calls private.