In spite of their convenience and necessity, cell phones are now another means whereby we can irritate our fellow man. Theaters, restaurants, trains–even public restrooms–are no longer safe from the possibility of an untimely call. Two weeks ago I even heard someone having a cell conversation in a toilet stall. At that moment I knew that if ever there was a reason for voicemail I had found it.

Somehow cell phone ownership seems to affect common sense. And on a more serious note, poor cell phone etiquette can ruin a career. Are you committing any of the following sins?

Sin 1: Annoying or Cutesy Rings

The cha-cha, the latest pop single, your lover’s voice–I don’t want to hear any of these, and neither does anyone else. Have mercy on the general public when picking a cell phone ring. Your latest Romeo saying, “Ooh, baby, baby” may be funny to your friends, but it’s a credibility wrecker at the office. Believe it or not, that actually happened to a friend of mine. She went to a business meeting and forgot to turn off her ringer. Midway through the meeting, her purse started talking. She had a fancy ring that was a recording of his voice telling her how beautiful she was. Thank goodness he didn’t use her name, so like everyone else, she pretended she didn’t know the source of the mysterious voice.

Sin 2: Holding Court

“We just landed, and I’m waiting to get off the plane.” I must hear that from at least four or five people every time I take a flight. In the midst of all the benign information that follows, what these rude cell phone users don’t say is, “There is a short, homicidal looking woman standing next to me. I can tell that she is getting ready to beat me senseless for talking loudly about nothing on my phone.” People, please: if there is nowhere for the rest of us to go, think about whether you really need to have that conversation.

Sin 3: We Can Hear You

For whatever reason, many people talk at top volume when they are on a cell phone. Microphones are sensitive. The person you are calling can hear you. We don’t need to. Enough said.

Sin 4: Your Help Is Ruining My Conversation

In the last few months, I have seen signs in fast-food restaurants and retail stores that say something to the effect: “We will gladly help you when you are done with your cell phone call.” It doesn’t surprise me. Many times I have watched people talk on phones while in line (see Sin 2) and then not even address or acknowledge the employees whose assistance they need. Simple courtesy will go a long way toward getting you on your way.

Sin 5: Taking a Call When in a Meeting

As the old saying goes, just because something can be done doesn’t mean that it should be done. Whether you have called it yourself or are merely attending at someone’s request, invitation, or order, a scheduled meeting is not the time for cell phone calls. The rings alone are intrusive; answering them is an even worse breach of etiquette. The message received by those at the meeting is that they are less important than the disembodied voice coming through the cell. Unless your intention is to make others feel insignificant (definitely not a cool move if your boss is waiting for you to get off the phone), then don’t answer, turn it off, and get it out of sight.

Sin 6: Are You Talking to Me?

With the invention of hand-free cell phones came the double-edged sword of convenience and mistaken identity. Who among us has not been taken aback by the presence of another human trawling the aisles of Wal-Mart while actively engaged in what, on initial inspection, would seem to be an animated discussion with himself or herself? After giving this person, who is clearly having a psychotic episode, a wide berth, we realize there is actually a streamlined headset attached to the person’s skull yet well hidden underneath a hat. At the risk of being mistaken for a pop singer or air traffic controller who has wandered away from work, leave the headset in the car.

Sin 7: Too Much Information

Discussing anything of a private nature that others within earshot might be able to hear is unwise on a number of counts. Think about it: do you want your coworkers to know the results of your latest lab tests your doctor’s office has just called to share with you? or see your “dark side” when your contractor calls to tell you his work will take two months longer and $2,000 more than he had originally stated? or hear your travel agent has booked you on that cruise to Nassau for the same week you’d requested to have off for surgery you so desperately needed? Unless you want to raise a lot of questions and eyebrows, take calls from those who probably have unpleasant, upsetting, or incriminating information when you have total privacy.

On a very serious note, too much information given over a cell phone while others are in your presence could cost you dearly. A friend recently shared with me his experience of standing behind a woman talking on her cell to a repairman who was coming to her home to do some work while she wasn’t going to be there. By the end of the call, my friend had learned the woman’s name, address, neighborhood (complete with directions on how to get there), and the location of the spare key she had left for the repairman to gain entry to her house. Had he been so inclined, he could have reached the woman’s place before the repairman and cleaned her out—or worse.

Go forth, and sin no more. These tips just might save you your credibility, image, job, belongings—even your life..