(FORTUNE Small Business) – It's fashionable to complain about today's lack of cellphone etiquette—the person who jabbers away in a restaurant or takes a call during an important meeting. But what matters more in business—and is often overlooked—is the courtesy and efficiency of your employees when they use old-fashioned office phones to deal with customers.

I made a call recently to inquire about the services of a particular business. "Hello, will you please hold?" was as far as the call went—and it took less than half a second. The next sound I heard was elevator music. The recipient of my call didn't have the courtesy to wait for my response. He didn't even announce the company name—how was I to know I had dialed correctly? He expected me to watch my cellphone rack up minutes while my ears were abused by a Muzak rendition of "Margaritaville."

I thought to myself, Screw this! Click.

Have you ever wondered how much business you might be losing because potential customers don't last past the first impression your company gives? Despite the growth of contacts through e-mail and your website, neither is as important, especially to a small business, as the telephone. E-mail doesn't offer the depth or emotional intonation that a phone call does. Many e-mails come off as cold, patronizing, or incomplete, even if that is not the intention. And your website, even if somewhat interactive, will never replace the communication that takes place over the phone in a one-on-one conversation.

Used effectively, the phone can be a killer competitive weapon for a small company. A friendly voice on the line can give you a big advantage over giant competitors, which tend to give impersonal service. Whatever you sell, supply, or serve, the sound of the phone ringing in your office is nothing less than the sound of potential. It represents a potential new customer or further business from a previous customer or follow-up business from a favored customer. It's your only chance to make a good first impression. Even if good service requires hiring another employee or two, it's a small cost compared with losing a customer.

When you call my office—and that goes for every office I have ever operated—you are guaranteed to hear a cheerful hello, followed by my company name, and ending with the responding person's first name. This salutation not only makes it easy for our callers to initiate a dialogue but makes them feel welcome and ready to get down to business.

Once the greeting is complete, the employee must ensure that the caller gets what he needs—during and after the call. (One tip: Having a "frequently asked questions" page on the company website will go a long way toward making some customers happy without their even having to call.) If the caller has to be forwarded or put on speakerphone or placed on hold, he should be told so and given the opportunity to opt out. And any agreed-upon follow-up needs to be followed up—messages delivered, appointments scheduled, and callbacks noted. While it's important to talk a good game on the phone, it's that much more important to walk the talk once you hang up.

Anyone in your company who deals with the outside world—and that's just about everyone—should be trained in phone smarts. And we're not just talking politeness. Teach employees to distinguish between the valuable customer who calls in needing lots of advice and the time vulture who never buys but keeps your staff talking, wasting precious time. Teach your people how to paint a good impression through their words, actions, and passion. Try to communicate a positive feeling and ultimately a sense of confidence.

Finally, there's the goodbye. By concluding the conversation with quality assurance and positive closure, you'll be making the customer an offer he can't refuse.