By JoAnn Greco, for Yahoo! HotJobs

Cellphones are everywhere today, and there's no doubt that their omnipresence has introduced serious breaches of etiquette in business settings.

You're at a business lunch and before your associate even spreads the napkin on his lap, he slaps his mobile phone onto the table, next to his water glass. Or you're sitting in a meeting when you notice another attendee is actually texting.

Keep Phones Hidden

Such behavior violates what Scott Ginsberg, a St. Louis business communications consultant, terms "'the golden rule of interpersonal communication,' which is to make the other person feel like the most important one in the world." Cellphones should be restricted to two sites, Ginsberg suggests: on your body (pocket or belt loop) or easily accessible in your briefcase or bag. They don't deserve a seat at the conference or dining table.

Text-messaging or appearing to wait for a call while you're with someone else sends a signal that you have better things to do. That's bad news in any situation, but in business it could be a real deal-killer.

Professional use of cellphones demands special consideration, cautions Kate Zabriskie of Business Training Works in Port Tobacco, Maryland. "Cellphones share a common problem with email and Blackberrys in that they're all informal methods of communication," she says. "They make it easy for us to be sloppy. The crucial thing is to remember at all times that it's still business."

You Have an Audience

That goes double for when you're discussing company matters in a public setting, such as an airport or train station. "You'd be amazed at the confidential stuff I hear from my seatmates," Zabriskie says. "Be especially aware if you're carrying or wearing anything with your company's logo on it."

Another case where you might want to exercise caution is when using your mobile for calls you don't want coworkers to know about, like personal conversations or job interviews.

"People tend to talk louder on a cellphone, and that defeats the whole idea of holding a private conversation," Zabriskie observes. Similarly, consider those around you when choosing your ring tones. "The ring you pick is telling," says Zabriskie. "Do you really want everyone in your office to hear Barry White moan 'Ooh, baby, baby' every time a call comes in? Probably not."

Answer as a Professional

Not only do those around you deserve courtesy, so too do your callers. Since you're often not at your most comfortable when you take a cell call, be sure to let your caller know right away that they've reached you on the move. "That can be code for 'I can't talk very loudly' or 'I don't have a pen' or 'I may not hear everything you say,'" says Zabriskie.

Finally, remember to answer your cell in a businesslike manner, not by shouting "Yo." This is especially true if you expect to be contacted by any potential employers for a phone interview.

"Think of it as the first impression a caller gets of you," says Zabriskie. "If you give your cellphone number out for professional purposes, then you better sound professional when you answer it. If you use it mainly for personal matters, it's best to keep it shut off during work hours."