I was waiting in line at my neighborhood bookstore when I became aware of a struggle going on behind me.

“I thought I told you to turn that thing off,” snapped a woman in gray slacks. She was scolding her son, whose cellphone was ringing. I hadn’t even noticed the sound – a sad testament to how cellphones have become woven into the tapestry of everyday life.

The kid – high school age, scuffed sneakers and baggy jeans – started fumbling around in his backpack, trying to find the offending item.

“Out!” his mother commanded. “Go wait in the car.” She practically threw her keys at the boy, who slunk out the door.

To my surprise, the woman turned to me and apologized. “I don’t mean to yell. I’m just so fed up with cellphones!”

The woman – who introduced herself as Beth – explained that she teaches math at a local community college. And, she told me, she is constantly reprimanding her students for paying more attention to their cellphones than to their work.

“This morning,” she said, “one student actually answered her phone to tell the caller that she was in the middle of a calculus test! And even if they turn off the ringers, they still text one another.”

The blatant use of cellphones, anywhere and any time, has become commonly accepted behavior.

Perhaps that’s why Beth’s students seem to be unaware of what they are doing. And while I’ve never personally experienced such an egregious display of rudeness, I have noticed that most people have few to no manners when it comes to their mobile phones.

It’s the damnedest thing. You are having a conversation with someone, their cellphone starts ringing, and – without even excusing themselves – they pick it up and start talking to someone else. You stand there, feeling like a fool … and wait.

Cellphone calls routinely disrupt personal conversations, business conversations, meetings, speeches, ceremonies, and even religious services. The only attempts made to curtail this modern menace are in theaters and concert halls – as if entertainment were the only thing more important than instant communication.

In the old days, we followed an informal set of rules. The first rule was universal: Except in dire emergencies, ongoing conversations should not be interrupted. If you wanted to say something, you would wait your turn. There was also a rule that related to the intensity of the conversation: The more serious it was, the stricter the prohibitions against butting in. And, finally, there was an acknowledged hierarchy: Children deferred to adults, students to teachers, employees to their bosses, and so on.

Call it respect … call it courtesy … all that is out the window. Any conversation, regardless of how important, intimate, or urgent, is now brought to a screeching halt the moment someone’s phone goes off.

Of course, I am something of a hypocrite when it comes to most causes I advocate – and this one is no exception. Although I feel mistreated when someone I’m speaking with answers his cellphone, I have the strongest urge to answer mine whenever and wherever it rings.

Most of the time, I’m happy to say, I resist the temptation. My phone is set to vibrate before it starts ringing. So if it starts vibrating during a conversation, I reach into my pocket and cancel the call.

But few people have any sense of manners when it comes to their cellphones. Which is why I’d like to offer you six rules for polite cellphone use:

1. If you must be available to callers, put your phone on vibrate. Leave the room to talk if an important call comes in.

2. Never talk on the phone while conducting business face to face with someone else.

3. If the lights are out, turn off your phone. Audiences in playhouses, theaters, cinemas, and observatories want to concentrate on what they’re watching/listening to.

4. Keep your voice down. No need for everyone in the room to hear what you’re saying.

5. Do not discuss private business or personal matters in the presence of other people. Put the caller on hold and move to an isolated area. Or reschedule the conversation.

6. Don’t bring your cellphone to job interviews, weddings, funerals, church, business meetings, presentations, court, museums, or the library.

Follow these suggestions and your friends and colleagues will appreciate your full attention. Your fellow theater-goers will appreciate your silence. And you and your dinner companion will enjoy an uninterrupted meal.