PORTLAND, Ore.—Don't set a midnight deadline to evict Occupy Wall Street protesters -- it will only give a crowd of demonstrators time to form. Don't set ultimatums because it will encourage violent protesters to break it. Fence off the parks after an eviction so protesters can't reoccupy it.

As concerns over safety and sanitation grew at the encampments over the last month, officials from nearly 40 cities turned to each other on conference calls, sharing what worked and what hasn't as they grappled with the leaderless movement.

In one case, the calls became group therapy sessions.

While riot police sweeping through tent cities in Portland, Ore., Oakland, Calif. and New York City over the last several days may suggest a coordinated effort, authorities and a group that organized the calls say they were a coincidence.

"It was completely spontaneous," said Chuck Wexler, director of the Police Executive Research Forum, a national police group that organized calls on Oct. 11 and Nov. 4. Among the issues discussed: safety, traffic and the fierceness of demonstrations in each city.

"This was an attempt to get insight on what other departments were doing," he said.

From Atlanta to Washington, D.C., officials talked about how authorities could make camps safe for protesters and the community. Officials also learned about the kinds of problems they could expect from cities with larger and more established protest encampments.

In Portland, for example, protests were initially peaceful gatherings. Then the city's large number of homeless people moved in, transforming the camp into an open-air treatment center for drug addiction and mental illness.

On Oct. 11, just five days after protesters set up camp, police chiefs who had been dealing with the encampments for weeks warned that the homeless will be attracted to the food, shelter and medical care the camps offered.

There were more tidbits, including the midnight deadline.

City police did exactly that when they evicted protesters during the day from two downtown parks over the weekend. Officers came armed with pepper spray, bean-bag rounds and stun guns, but didn't need to deploy them.

One protester says he was injured when he fell and police dragged him from the scene.

Going in at midnight "would have been a confrontation that really wasn't necessary," police spokesman Sgt. Pete Simpson said.

It was advice that came after the Oakland, Calif., protest was shut down Oct. 25 in a confrontation that turned violent. One protester, Iraq War veteran Scott Olsen, was badly injured.

In that city, where protesters' encampment was peacefully removed on Monday, city officials took part in strategy sessions with other big cities dealing with similar demonstrations.