(A quick note before we get started. I wrote the following in response to reader feedback to another column: 10 Bad Habits That Make You Look Really Unprofessional. This post is the counterpoint to that one.)
Here's a story from about 15 years ago. I was traveling from Seattle to Yakima for work, flying in a tiny commercial turboprop. There were only 10 or 12 passengers, and the cockpit was separated by a curtain rather than a door. We flew through the Cascade mountains in really rough weather, and the captain -- a pilot in his early 20s -- pulled the curtain aside.
"The tower is saying it's our choice to continue to Yakima or turn around," he yelled over the din of the engines, "But I think we're gonna give it a try."
What’s wrong with this picture, right? "I think" and "Give it a try" are pretty much the last things you want to hear a commercial airline pilot say, especially in a bad storm. My fellow passengers nearly revolted. The pilot quickly changed course (both literally and figuratively), and we flew back to Seattle.
I've told that story a few times over the years, usually for laughs. But remember: It wasn't the storm or the tiny plane or the air traffic control's apparent laissez-fair attitude that freaked us passengers out. It's that the pilot's attitude made him seem totally unprofessional -- and we all lost confidence in him.
Here are a few of the attributes you can demonstrate to make yourself seem more professional. I’m not saying they’re easy, but they are pretty simple. (Keep in mind, nobody demonstrates them all constantly. You’re only human. Just try to be the best human you can.)

1. Confidence

This was the biggest problem with the pilot's performance that day. Confidence without the ability to back it up is useless, but if you’re truly competent, own it.

2. Candor

Truly professional people are forthright. They assess the situation, calculate the risks, and offer a truthful opinion.

3. Self-awareness

This is a part of displaying confidence -- knowing who you are and where you fit in the world, and owning your strengths and weaknesses. If you do that, you can work to buttress the things you don't do as well.

4. Strategic thinking

One of the basic tenets of success is to start with the end in mind. Truly professional people identify their goals, then work backward to achieve them.

5. Anticipation

Be like Radar O'Reilly. Wait, you probably don't get that reference, because most people reading this probably weren't watching the television show M*A*S*H in the 1980s. (See? Self-awareness.) No problem. Just know that focusing on others' needs to the point that you can anticipate their challenges and solutions breeds confidence.

6. Caring

Related to anticipation: You can't truly help others if you can't bother to learn about their goals and fears.

7. Realism

"Promise me the world," the song goes. That may be a way to get the boy or girl of your dreams to pay attention, but it does nothing to make you look professional. Instead, promise the most you can, consistent with your ability to deliver.

8. Follow-through

See what I mean? These attributes are simple but not necessarily easy. Say you'll do something, then do it.

9. Enthusiasm

This one is inspired by reader comments, when I said Pollyannaishness was unprofessional. Smart enthusiasm, on the other hand, is a very positive quality. Colin Powell put it best: Perpetual optimism is a force multiplier.

10. Diligence

This is related to follow-through, but it's not exactly the same thing. Be persistent, demonstrate worth ethic, and "check small things." (That’s another Powellism, come to think of it.)

11. Performance

Nothing says "professional" like accomplishments, especially repeated accomplishments over time.

12. Discretion

Caring and self-awareness, combined with good communications ability, leads to prudence and the ability to be candid without giving offense.

13. Curiosity

No professional is ever finished learning. ‘Nuff said.

14. Risk-taking

I hesitated to put this on here, out of fear of giving the wrong impression. Risk-taking doesn't mean being risky in the negative sense. Instead it’s about the realization that all courses of action involve some risk, and balancing that realization against the paralyzation of inaction.

15. Humor

You don’t need to be hilarious, but you need a sense of humor; it demonstrates perspective.

16. Fitness

This is unfortunate but true. If someone looks as if he or she doesn’t care about their health, it’s a lot harder to project professionalism -- and with it, the notion that they care about other things.

17. Authenticity

It’s good entrepreneurial advice to “fake it till you make it,” but your performance needs to be grounded in truth. Otherwise, no matter your skills, your deficits, your interests -- or frankly, even the things you aren’t interested in -- people can tell.