In the history of spectacular career flame-outs, it's hard to match A.J. Clemente's infamous first day f-bomb as a local news anchor.
(Yes, he was fired.)
While some career killers are clear and follow common sense, the workplace can be rife with hidden dos and don'ts.
"There are lots of different ways to get fired, and sometimes you'll never know what you did wrong," said Cynthia Shapiro, a former human resources executive and the author of "Corporate Confidential."
What's more, these secret no-nos can be behaviors people think are good, morally and professionally.
Click through the list of potential secret sins, and watch the full story on "20/20: Work War: How to Win It, How to Wage It" on Saturday, Feb. 1, at 10 p.m. ET
"Being popular can erode your job security very quickly," Shapiro said. "It leads to sharing too much personal information at work."
"I have sat in meetings where the CEO or the higher executives said, 'I heard this person is going through a nasty divorce; let's not promote them.' ... Friendships need to be very strategically crafted."
|Bringing Yummy Treats for Colleagues|
"This is particularly a mistake for women," said Dr. Lois Frankel, author of "Nice Girls Don't Get the Corner Office." To be taken seriously, she said, leave the baking to Betty Crocker.
"It's a nice thing to do," Frankel said. "[But] if you do it too much, you'll just be seen as the mascot, or the department mom, and you don't want that."
But at the XO Group, formerly The Knot, executives Lori Richmond and Alison Bernstein proudly call themselves office moms. They bring cupcakes to work, keep the candy jar full and maintain the office birthday calendar.
And their boss loves it.
"We are almost 70 percent women," said Carley Roney, co-founder of the XO Group. "For us to be, like, sensitive and caring and encouraging -- and motherly, if you are gonna call it that -- is part of what's made us successful."
"If you're in a culture like the Knot, by all means do it," Frankel said. "But in some cultures, that's just going to completely be a no-no."
Studies show that dividing your attention between tasks can decrease efficiency and accuracy, Shapiro said.
"Companies say multitasking is what they want. It's not really what they want. What they really want you to do is focus in with laserbeam focus on one thing and then switch to another and switch to another and switch to another," Shapiro said.
|Talking to HR|
Even though your company may say it's best to take your troubles to HR, that can hurt you, Shapiro said.
"They don't work for you; they work for the company. The company cuts their paycheck," Shapiro said.
Most people assume that what they tell HR is confidential. "All that means is, they are not gonna blab it to the other employees. But they will absolutely tell your boss," Shapiro said.
|Overdecorating (Especially Troll Dolls)|
"Companies will say, 'Here is your space' ... do whatever you want with it," Shapiro said. "It's kind of an unconscious test of loyalty and values, because if you fill it with troll dolls or crystals or religious things, it's gonna make them feel really, really uncomfortable."
And don't go crazy with family photos.
"It's telling the employer that this person would rather be at home with their kids," Shapiro said. "One professional shot, and that's it."
|Bringing Kids to Work|
"It's really not a good idea unless you can guarantee that your kids will be absolute angels," Shapiro said. "If your kid decides to have a temper tantrum, it will reflect on you. 'If he can't control a child, how's he going to manage the company?' That kind of thing."
|Working Too Hard|
Believe it or not, burning the midnight oil can backfire. Research shows over-working can decrease performance, because it deprives you of sleep. Most bosses don't care how long you work -- just how much you get done.
"Working 24/7, where you're always accessible, where you just kind of seem harried because there's always so much to do -- you're not seen as someone who manages their time well," Frankel said.
With so many rules, how can you be comfortable being yourself and doing your job?
Paradoxically, that's the whole point of knowing the hidden rules, Shapiro said.
"It's easier to be yourself if you know where the land mines are," she said. "It's actually very empowering, and you can make really good choices."
Watch the full story on "20/20: Work War: How to Win It, How to Wage It" on Saturday, Feb. 1, at 10 p.m. ET