(FORTUNE Magazine) – Looking back at the summer's biggest business story, one question lingers: How did United Parcel Service--the $22 billion colossus that sits perennially atop FORTUNE's list of most admired corporations--lose the battle for public sympathy with the Teamsters union, whose very name tends to evoke images of violence and corruption? The simple answer is that the company's managers--half of the top 12 are ex-teamsters--were astonishingly naive. Explains UPS vice chairman John Alden: "We didn't expect a strike. Then we thought it would last only a day or two. And we thought the vast majority of our workers would cross picket lines."

That spectacular misjudgment reflects just how insulated the employee-owned company's managers are (its corporate culture is described variously as "cultlike," "militaristic," and "unimaginative"). UPS was an ideal union target. When the lights came on, CEO James Kelly was without a strategy, outmaneuvered at every turn by the slick performance of Teamster president Ron Carey. It was a public-relations fiasco.

Crisis-management and PR professionals are sifting the record for lessons. Here are four:

--Rule No. 1: Never underestimate your opponent. Teamster membership has just leveled off after shrinking for 16 years, and the newly reelected Carey was vulnerable. Because two consultants had been indicted for funneling more than $220,000 in union funds to his campaign, Carey's recent election was about to be nullified. Carey needed a big win, and he prepared carefully.

--Rule No. 2: Don't let your opponent frame the issue. The Teamsters found a hot button--Americans' resentment toward corporate managers for holding down workers' wages at a time when profits and executives' salaries are soaring--and pushed it to spectacular result, depicting UPS' 110,000 part-time workers as victims of insecure jobs and low pay. Concedes Alden: "Carey wrapped himself in the American flag, and his message resonated. We couldn't successfully fight his emotional arguments with logic." (Don't think your company couldn't be attacked. Warns New York PR guru Gershon Kekst: "Every company in America should pay attention to what happened to UPS. Corporate loyalty is dead, but managements don't know it.")

--Rule No. 3: Be prepared. "Companies must have plans developed in advance to cope with crisis," says Richard George, who heads PR for the Society of Public Relations. To that end, Richard Hyde, who directs Hill & Knowlton's crisis-communications practice, warns that 75% of serious problems arise slowly. He helps clients set up early-warning systems to detect possible sparks, such as an upcoming labor negotiation.

--Rule No. 4: Get your story straight. Once a crisis has engulfed a company, experts say there's a fundamental rule that is violated only with dire consequences: one spokesman should handle all communication with the public. And they recommend that the person be trained in how to deliver a few unified and simple messages. Says Hyde unequivocally: "There is nothing worse than having two spokespeople." UPS damaged itself by allowing as many as a dozen human-resources executives to answer questions from the press. The scattered approach prevented the company from pounding home a few points, such as: "Why won't Ron Carey allow the union to vote on our proposal?" Similarly, when UPS tried to shift the focus from the plight of part-time workers to the question of whether the company should take over management of workers' pension funds, eyes across America glazed over. Details were too complicated. Says an executive who has run communications during his company's labor negotiations: "UPS had many people delivering messages that jumped around. It's too bad, because the company had a great story to tell."

Some experts can find nice things to say about UPS. Crisis consultant James Lukaszewski, for one, gives the company high marks for not replacing workers and for focusing on a settlement. "You don't have to mount a counteractive grassroots or media campaign," he tells clients. "It's what's said at the bargaining table that counts."

Maybe, but don't tell UPS. Vows vice chairman Alden: "The next time, we'll prepare for a multilevel grassroots political campaign, not a traditional labor-management dispute."

--Linda Grant