An ancient Greek philosopher named Epictetus once observed that we have two ears and one mouth so we can listen twice as much as we talk. Unfortunately, that advice too often falls on deaf ears — which subsequently squelches opportunities for employees' professional growth and hurts workplace productivity.

"Listening is the most important yet underdeveloped skill for personal and professional success in what I call today's 'new normal,' yet it's never formally taught," says Alan Adler, an organizational-performance consultant, business speaker, and the author of Upstream and Getting the Fish to Swim to YOU and Keeping Them In YOUR Boat (www.alan-adler.com). To underscore his point, Adler notes that the American Management Association offers more than 300 communication courses, but only two that cover listening skills.

"The only way we can improve our listening skills is to understand the barriers to good listening and how to overcome them," he continues. "Many people don't realize that if they're a good listener, people are more likely to listen to them. And in today's 'new normal,' being a good listener is a great way for people to rise above the clutter and get noticed in a positive way, both personally and professionally."

So how do we become better listeners? Adler suggests focusing on the three C's: concentration, content and collaboration. The first refers to our biggest barrier to listening — staying focused on what someone is saying. The second refers to trying to understand what is being said, and asking questions that show you've been listening (as in, "If I understand you correctly, you're saying that ..."). And the third involves not just listening to support your own understanding, but also being open to other people talking and enabling them to do so, along with asking questions and providing feedback that indicate you're engaged, Adler notes.

Adler also contends that listening is not necessarily a skill, but a choice. So you need to make a conscious decision that when someone talks to you, it's important enough to warrant your undivided attention. Sounds easy enough, but in reality, it takes effort and discipline.

"Listening is a choice we make every minute of every day," Adler says. "We're all capable of listening, but it requires a conscious effort. We have to fight to do away with distractions and assumptions ... and give a speaker time to finish, and wait to pose questions at the end, not before the speaker is finished. Interrupting someone before they finish speaking is rude and disrespectful."

To emphasize the point, he points to one of his favorite cartoons, which shows a group of people talking with a caption that reads: "Oh, I'm sorry. I didn't realize the middle of my sentence was interrupting the beginning of yours."

Speakers are responsible, too

However, the responsibility is not only on the listener, Adler suggests. The person doing the talking or making a presentation also must bear some of the responsibility for good listening by making their message more listenable. "My message is more holistic than just walking away with a list of six things that can make you a better listener," he notes.

For example, when you make a presentation at a business meeting, Adler says it's important to keep in mind that in most audiences, about 30 percent of the people are left-brained thinkers, or more analytical and logical, while the rest are right-brained, or more inclined to be creative types.

"So you need to make certain that you have enough charts, facts, graphs and empirical evidence to satisfy one part of the audience, along with poems, songs and photos to reach the other 70 percent," he says.

Adler also encourages messages with "more signal and less noise." In other words, cut down on things like acronyms and jargon that people may not understand, and instead speak in simpler, more easily understood terms.

"Most use acronyms because they think it's faster or cute," he points out. "But in reality, if people don't know what they mean, they instead create their own meaning for it. If someone doesn't ask what it stands for, they're likely to miss the point ... yet another reason why we only retain about 5 percent of what's said. That's a big problem."

Body language is also important, he says. For example, if you talk with you arms folded or put your weight back on one leg, you're subtly sending non-verbal cues that your message may not be credible.

"People take in subtle cues not only from the volume of what you say and the passion with which you say it, but by your body language," he says.

How do you know if people are listening to you? Whether you're talking in a one-on-one conversation or making a presentation, it's not rocket science — take your cues from visual clues. Are they avoiding eye contact with you? Glancing down at a cellphone? Showing no facial expression? Interrupting you and presuming to know what you'll say next? Quickly changing the topic when you're finished talking? All of these signals indicate an unengaged person or audience that's not picking up what you're putting down. And if you do the same things while someone else is talking, you're not exactly headed for an A grade in Listening 101, either.

In today's world, listening — and making yourself more listenable — is more challenging than ever. We face an unprecedented number of choices on numerous levels every day; as Adler notes, even something as simple as buying toothpaste these days involves selecting from an incredible array of options. And the 24/7 bombardment of marketing messages from multiple kinds of platforms, from traditional media to Twitter and Facebook, makes it difficult to focus on listening — or make your message heard above the din.

But with discipline and focus, you can become a better listener and keep the attention of your audience.