So you've finally graduated from college and landed your first real job.

But do you know the dos and don'ts of workplace etiquette?

No? Well, I'm also a little rusty when it comes to knowing how to conduct myself appropriately at work.

(My personal workplace indiscretions include snapping gum and blowing huge bubbles, which distract co-workers when they witness the bubbles burst, and the subsequent ritual of trying to peel the sticky stuff off my face or untangle it out of my hair.)

So I asked three workplace etiquette professionals what they thought were the worst faux pas that young employees, as well as veterans, should avoid. Then we compiled the most heinous to create the Top 10 etiquette errors.

We talked to Dee Hurst, director of human resources at the University of Iowa's Tippie College of Business; Mary Mitchell, author of "Class Acts: How Good Manners Create Good Relationships and Good Relationships Create Good Business" (M. Evans & Co. Inc., $15.95); and Dale Cyphert, associate professor of management at the University of Northern Iowa.

1. Forgetting your cyber-etiquette. "A lot of new grads get nailed in their career early for sending really too casual e-mails," Hurst said. An e-mail is still a written document that can be printed and forwarded, so use proper grammar and check your spelling. As a rule of thumb: Visualize any e-mails you send as also going to a manager two levels above you, Hurst said. Also nix the online abbreviations, and save the "emoticons," which use punctuation to express emotion, for text messages to your friends.

2. Not observing corporate culture. What do people wear to the office? What time do people come to work? How late do people stay? Your ability to observe and fit into your work environment has a huge impact on your professional and personal happiness, Hurst said. "Most people come in with the requisite skills to do the job, but then once they're in, it's also how they fit into the environment."

Being uncomfortable in work surroundings can lead to what Hurst calls a "failure to thrive."

3. Overusing slang. "I think young people forget to watch their language," said Mitchell, who discusses the "Ten Most Common Business Mistakes to Avoid" in her book. Excessively saying, "like," "Oh my God," "you know," and "whatever," in the workplace tarnishes your image of professionalism, Mitchell said. "They risk not being taken seriously."

4. Dressing unprofessionally. This generation of new workers has been raised in such a casually dressed environment that "they don't realize how far off the mark they are," Cyphert said.

Dressing appropriately is especially crucial with the increase of international business.

"Americans are incredibly casual compared to international folks," she said. "People in the business environment see it as a huge sign of disrespect."

One tip is to look at what people a level above you are wearing to work, Hurst said.

5. Not minding your manners. Do you fail to say "please," "thank you" and "excuse me"? That's a no-no. "We are so attached to producing and performing that we've really forgotten that it's important to be a decent human being, first and foremost," said Mitchell, president of the Mitchell Organization.

6. Having a negative attitude. According to Mitchell, this is the most common business mistake, and includes being impolite and taking out frustrations on unsuspecting co-workers.

"We really forget to put ourselves in the other person's shoes. We really forget that our behavior has an effect on other people," Mitchell said.

Before you fly off the handle, she said, take a second to be by yourself. Go hide in a bathroom stall, close the door, count to 10 and take deep breaths.

7. Choosing the wrong friends. While it can be tough making friends in your new job, be careful not to glom quickly onto just anybody, Hurst said.

Avoid becoming buddies with someone who is on the outs with higher-ups who are in a position to affect your career, she said. "Be friendly, but get the lay of the land in terms of people's position and history with an organization."

Hurst said hanging out with someone on shaky ground with bosses may short-circuit the development of contacts.

8. Being late. A lack of punctuality is a sign of rudeness. Cyphert said showing up for an appointment when you say you'll be there shows respect for people's time.

9. Carelessly mixing business and pleasure. "Work is not college," Hurst said. "So the mixing of business and social relationships can be fraught with danger." Yes you can socialize, but always maintain a certain level of professionalism, Hurst advised. That can be tough after your third gin and tonic during happy hour with your colleagues, so beware of those loose lips and keep your words and actions in check.

Hurst's take on office romances: "That's a career killer."

10. Leaving the coffeepot empty. If you've just poured yourself the last cup of coffee, make the next pot, Cyphert said.

Also remember to be tidy in the break room — clean up after yourself, cover your food in the microwave so it doesn't splatter and don't leave food in the refrigerator until it turns green and fuzzy.