Attendees of Fortune‘s Most Powerful Women Summit in Laguna Niguel, Calif. got just that on Tuesday as four experienced corporate directors shared lessons they’ve learned from years at the boardroom table.

Each was asked to reflect on what they’d taken away from some of their earliest director stints.

Renée James, chairman and CEO of Ampere Computing who’s on the board of Citigroup, Oracle, Vodafone, and Sabre, said it’s vital to understand “how current directors work with the CEO.” You need to know, she said, “what dynamic you’re getting into.”

Pat Russo, chairman of Hewlett Packard Enterprise and director at General Motors, Alcoa, Merck, and KKR, had this simple advice: “You really want to be on a board where you can be engaged.”

For Susan Schwab an early experience taught a rather harsh lesson. The professor at the University of Maryland School of Public Policy is currently a director at Boeing, Caterpillar, FedEx and Marriott. Years ago, she was on the board of Calpine Corp., which went bankrupt in 2006. Her ties to the company were a factor in the withdrawal of her nomination as President George W. Bush’s commerce deputy secretary. She said on Tuesday that she eventually discovered “there were some things they were not telling the board.”

Transparency—or lack thereof—also factors into what Ellen Kullman learned from her early board tenures. The retired chair and CEO of DuPont is now a director at Amgen, Dell, Goldman Sachs, and United Technologies Corp. At the Fortune MPW Summit, she warned against assuming that information—whether about activist investors or other matters—is being spread among directors in an egalitarian way. Had she realized that was not always the case, she says she might’ve “stepped into” more situations.

Fast forward to today’s boards, and Russo says they’re making progress on the transparency front. “CEOs who are the most confident are the most transparent,” she said. “When you have that, [directors] have the opportunity to engage around the reality of what a CEO is dealing with. More and more CEOs I work with are like that.”

That higher level of transparency comes at a time when the role of corporate director is arguably more complex than it’s ever been as boards contend with challenges like activist investors, cyber threats, and divisive social issues that have the potential to damage a company’s reputation, not to mention its market value. In speaking of the #MeToo movement and the need for directors to know of internal complaints, Kullman put it bluntly: “Board members don’t want to be embarrassed by shoving something under the rug.”