“Retirement passed me by,” the late great Helen Gurley Brown told Cathie Black back when the two worked together at Hearst. Black headed Hearst Magazines for 14 years until 2010, while Brown, into her 80s, was the ever-present grand dame of Cosmopolitan.

Brown, who died on Monday at 90, didn’t invent Cosmo, but as its editor from 1965 to 1997, she created the wonder that is now the top-selling U.S. monthly magazine, with 64 customized editions around the world. Her intoxicating work style (her office had pink walls and leopard carpeting) and provocative content (“fun, fearless, female” is Cosmo‘s motto) diverted attention from the reality that Brown had bona fide business chops. And the management lessons that colleagues took from Brown transcend the publishing world. Cathie Black offers three of the best lessons she learned from Helen Gurley Brown:

Care passionately about what you do—and do it the best you possibly can. “Helen believed no matter how small your job, if you approach it with passion and work beyond 9 to 5, doors will open for you,” Black says. The credo paid off for Brown, who reportedly had a slew of secretarial jobs before she moved up to writing ads. Helen’s break: At Foote Cone & Belding ad agency, she wrote such colorfully detailed, dazzling travel itineraries for her boss’s wife that the wife coaxed him to promote Helen from secretary to copywriter.

Treat everyone the same. “Helen said about people, ‘You never know who they are. You never know what they will become.’” Heaping kudos, recognition and respect on people–employees at every level–was Brown’s leadership approach. “She never thought any amount of praise was too much,” says Black.

Be personal and specific. Using her trusty Royal typewriter, Brown wrote letters constantly–hundreds each week in her heyday and dozens weekly in her later years. Each month, she critiqued Cosmo’s editions around the world. No matter that she couldn’t read the language; she appraised the layout, the photos, the typography of each edition and sent notes advising how to do a better job next time. Says Black: “Helen took the time to communicate in a way that no one does today.”