What's the difference between knowing what you're doing and the separate (but also quite useful) attribute of looking as if you know what you're doing?

We've explored this recently, when I wrote about the time I was on an airplane with a pilot whose cavalier attitude scared all of the passengers. (I don't know if he's good at flying planes, but I know we didn't trust him.) And about the guy who walked up to a group of us and swore several times in his first few phrases. (Is he good at his job? I don't know, because nobody was willing to give him a chance after that inauspicious start.)

Whether we like it or not, people make snap judgments about us all the time. So while it's crucial that you develop expertise, it's also crucial that you send the right signals that you deserve the confidence of others.

Among your most important tools? Your words. Here are a few to get you started.

1. "Here's our expertise."

This is about self-awareness and defining your limits ahead of time. In my case, for example, if you need to hire an amazing professional ghostwriter, I'm your man. Need someone to do your taxes for you? You're better off looking elsewhere.

2. "This is the plan."

A true professional has the knowledge and insight needed to assess a situation, and the skills and decisiveness to put together a smart plan. Decisiveness engenders confidence.

3. "I'll find out."

This is an attractive, proactive phrase that conveys both self-awareness and curiosity. You're confident enough to admit the limits of your knowledge, and professional enough to commit to correcting your ignorance.

4. "That's not possible."

Professional, but only in the right context. It's useful when you're confidently advising someone away from a journey that you believe (in your experience) will be a quixotic course of action. Caveats: a) You'd better be right; and b) it's an unprofessional phrase when uttered to undermine someone else's assertion of fact, as opposed to ambition.

5. "You can count on me."

At the end of the day, this is what we want to hear from anyone we hope is a true professional. "You can focus your attention on other things; I'll take care of this one."

6. "Here are the challenges."

If you can't articulate difficulties clearly, why would others have confidence that you'll be able to overcome them?

7. "Follow me."

These two words (the motto of the U.S. Army Infantry, by the way) succinctly communicate that you're confident enough to ask others to place their trust in you--even in life-or-death situations.

8. "Here's how it works."

True professionals understand that knowledge is meant to be gained and shared. Those who lack confidence are afraid that others will supplant their position if they share what they know.

9. "What else can I do for you?"

A true professional doesn't just work to the task; he or she examines the objective from a holistic perspective and offers solutions. Think strategically, not just tactically.

10. "I'll finish by tomorrow."

Or by close of business, or by 11 a.m. on Tuesday--whenever is appropriate. Deadlines matter.

11. "We screwed up."

Mistakes happen. A true professional acknowledges them--and (hopefully) offers ways to make things right immediately.

12. "Here's what we're changing."

No battle plan survives contact with the enemy; no business plan survives contact with the market. True professionals understand this, and are ready to revise when necessary.

13. "What do you think?"

How can you help other people achieve their goals if you don't listen actively enough to learn what they're really thinking and feeling?

14. "That's funny…"

Credit belongs to Isaac Asimov for this one: "The most exciting phrase to hear in science, the one that heralds new discoveries, is not 'Eureka!' but 'That's funny...'" True professionals are always expanding their knowledge and discovering new things.

15. "Let me level with you."

Honesty. It's such a lonely word--and it's mostly what we need from just about anyone we engage with in a professional manner.

16. "Job done."

Nothing communicates professionalism like results. To paraphrase Henry Ford, you can't build a reputation on what you're planning to do. (I know the headline says "15 Things"; no extra charge for this extra bonus item.)