A year or two ago when I was extremely busy and my phone was ringing off the hook, I found myself answering it all the time, at the expense of my family, friends and other clients. As I recall, it was during a casual conversation with another agent who told me that she never answers her phone while with a client that I made a vow to do the same.
Now I must say that I rarely picked up the phone during a listing appointment but I did answer a lot while with buyer/clients. I say rarely on a listing appointment because I make one exception to not taking calls and that is if it is from my daughter. The same is true if I am with buyer clients. I will pickup if it's my teenaged daughter. The other exception would be if the buyers have asked me to call the listing agent to ask a question and the lister is calling me back.
But phone etiquette is not just for realtors. It's for everyone. When you answer your cell phone while with some one else, it's like saying "You're not as important as this phone call", and that is not the message I want to convey. Here are some tips for all of us and ones I try to abide by, though I am by no means perfect.
Stay off your cell phone when you are in a line, such as in the grocery store, bank, or waiting to place a food order.
Stay off your phone while in a movie theater..sounds obvious, but people do it all the time, and remember to set your phone to vibrate.
With new technology like bluetooth, it's great when driving but it does not need to be in your ear 24/7.
If it's difficult to get back to someone in under 30 minutes, consider a message such as, "I can't take your call right now as I may be with a client, but I'll call back as soon as I can". That lets the caller know that you value and respect your clients.
These are just a few ideas for cell phone etiquette. I'm sure you all will be able to add a few more!