When President Obama first took office, female White House staffers developed a little trick for making sure they weren’t ignored in meetings, where two-thirds of the attendees were men.

They called it “amplification”: When one woman made a key point, another woman would repeat it, and give a nod to the source. Not only did it force the men to recognize a woman’s contribution, it prevented them from claiming it as their own.

The tactic worked to change the thinking among the men, according to a recent story in The Washington Post — including Obama, who began calling more often on women and junior aides.

“It just goes to show that these issues are so widespread,” said Jessica Bennett, author of the new book “Feminist Fight Club: An Office Survival Manual for a Sexist Workplace” (Harper Wave, 294 pp., $24.99). “Even the most powerful women in the most powerful office in the country had to do this stuff.”

Bennett, 34, is a contributing writer for The New York Times and lives in Brooklyn. Her so-called “click moment” came in 2010 when she was working as a staff writer at Newsweek. After being raised in privilege by liberal Seattle parents, taking AP classes and excelling in college, Bennett expected success to come easily.

“I felt really lucky to be there, but I wasn’t getting ahead,” she said. She struggled to get ideas approved, then saw them published under a man’s byline. Then she found out a male colleague at her same level was making $10,000 more.

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“I was frustrated for a long time, but didn’t vocalize it,” she said. Then she started talking to female colleagues who had the same experience.

They learned of a 1970 gender discrimination claim that 46 female staffers filed with the Equal Opportunity Employment Commission saying Newsweek had a policy of only allowing men to be reporters. The women won, and the victory “paved the way for female journalists,” Bennett said. (The case is the basis for a new Amazon Original Series, “Good Girls Revolt,” which premieres Oct. 28.)

Bennett and a colleague wrote about the lawsuit on its 40th anniversary, and through their reporting realized that not much about the office culture had changed.

It inspired her to form her own “Feminist Fight Club” — women who meet regularly to share war stories from the office, offer support, vet each other’s resumes, review job and salary offers, and take their unemployed members to lunch.

The book is chock-full of tools for women seeking to navigate the male-dominated office culture. Everything from how to negotiate a raise to creating your own personal board of directors to learning not to take the fall for mistakes that aren’t yours.

Bennett was sure to include plenty of statistics and facts that she verified again and again. The last 16 pages of the book contain 400 footnotes.

“I wanted to be bulletproof,” she said.

For example, women are interrupted twice as often as men. And if they speak a mere 25 to 50 percent of the time in meetings, they’re labeled “dominating.” Men are deemed “busy” when they refuse extra work, while women take a hit on likability when they push back.

In one study, researchers looked at mixed-gender teams, and found that people “inferred naturally that the best ideas came from men,” Bennett said.

Bennett sometimes treats the serious subject of workplace equality with lighthearted illustrations and cutesy humor: Terms like “Manterruption” to describe the way men cut women off when they’re speaking; or “Bropriator,” for men who try to take credit for women’s ideas.

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“Part of the reason I made up these stupid terms is to be tongue in cheek, but this stuff is so subtle and it’s really complicated,” she said. “To create a catchy name is a humorous way into it.”

It’s not all on men, Bennett said. Women can be sexist, as well.

“Women are highly competitive with one another,” she said. “They undermine each other.”

The problem is that there are few spots made available to women, she said. So they fight everyone for a shot.

“My perspective has been that if we even out the pie, there would be equal competition, rather than women working against each other,” Bennett said. “You have to support other women.”

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All that said, things are getting better. The millennial generation is much more aware of gender inequality, Bennett believes.

“The challenge is putting into practice the beliefs,” she said. “They want to be egalitarian and work with women, but they need to not just pay lip service.”