Charlie Riedel, AP
In this Aug. 17, 2014 photo, Michael Brown's mother, Lesley McSpadden, wears a don't shoot button during a rally at Greater Grace Church for her son who was killed by police in Ferguson, Mo.

FERGUSON, Mo. — Several dozen people gathered in a dim church basement here Thursday night to share plans for what to do if a grand jury chooses not to indict the white police officer who shot Michael Brown, an unarmed black teen, three months ago. Among their ideas: descend in large numbers on the nearby county seat of Clayton at 7 a.m. on the day after the grand jury’s announcement to snarl business.

A day earlier, a different group, chanting “no justice, no profit,” met in St. Louis to announce it will boycott the region’s retailers during the Thanksgiving shopping period as a response to Brown’s death.

Since August, a disparate array of demonstrators — some from longstanding organizations, others from startups with names like Hands Up United and Lost Voices — has been drawn here to protest not just the shooting of Brown, but also the broader issues of racial profiling and police conduct.

Now, with the grand jury’s decision expected in the coming days, the groups are preparing with intricate precision to protest the no-indictment vote most consider inevitable. Organizers are outlining “rules of engagement” for dealing with the police, circulating long lists of equipment, including bandages and shatterproof goggles, and establishing “safe spaces” where protesters can escape the cold — or the tear gas.

Yet the most important part of the planning may also be the hardest: how to prevent demonstrations from turning violent. Organizers say they want their efforts here to blossom into a lasting, national movement. So they say they hope for the protests to be forceful, loud and unrelenting — without the looting or arson that could undermine their message. But they also know that some among the ranks may be more volatile and harder to control.

“We’ve come to the conclusion that we really don’t want violence,” said one organizer with Lost Voices, who goes by the name Bud Cuzz. “We want to fix this. We still want to fight to make the laws change. We still want to raise awareness. But we don’t want the city to turn upside down.”

Montague Simmons, a leader of the Organization for Black Struggle, said there was a growing circle of demonstrators with “a clear message about what we are about and what kind of behavior we are looking for.” Yet beyond their carefully orchestrated plans for a series of shows of protest and civil disobedience, leaders here acknowledge that there are disagreements about what form of response is fitting and whether militant acts might spill over into violence.

“There’s a lot of anger out there,” Simmons said. “There’s nothing we can do to control that.”

At least one group has said on Twitter that it was offering a reward for information on the whereabouts of the officer, Darren Wilson, and, at another point, that it was “restocking on 7.62 & 9mm ammo.” Law enforcement authorities said they would not discuss individual groups, but that they were “constantly looking,” at several groups, according to Brian Schellman of the St. Louis County Police, “trying to separate the rhetoric from the actual threats.”

Immediately after Brown’s death on Aug. 9, protests began. For days, people marched and chanted along West Florissant Avenue, not far from where the shooting took place and, for brief periods, the protests grew violent. Stores were looted, and the police said demonstrators threw gasoline bombs and tried to set fires. The police used tear gas and rubber bullets.

Protesters said the police response was an overreaction to just a few in the otherwise peaceful crowd.

Though the confrontations quieted, the demonstrations have continued nearly nightly since. About 50 organizations, including Simmons’, have joined forces in a “Don’t Shoot Coalition,” and the level of planning is intense.

In dozens of training meetings like the one held at the church here Thursday, demonstrators have been given lists of items to keep at the ready for when a decision is announced: gloves, maps, protest team names and phone numbers, medical supplies and a “jail support number,” in case of arrest, to be written in permanent marker on a protester’s arm. Leaders have shared text alert numbers to keep in constant contact.

They have announced safe spaces in area churches where leaders say protesters can warm up and stay clear of the police, as well as “hot spots,” locations around Ferguson where demonstrations seem likely. In another indication of the level of planning going on, some leaders say they intend to carry out their acts of protest even if the grand jury brings charges against Wilson to show that the issues raised by this case reach beyond a single shooting. One more sign of the elaborate organizing: the group Hands Up United has produced its own polished video.

And they have proposed 19 “rules of engagement” with law enforcement authorities, including tolerance for “more minor lawbreaking” (like thrown water bottles) and 48 hours of notice for the protesters when a grand jury decision comes in. Some of the rules have been granted during talks with law enforcement authorities, leaders said, but others have been rejected.

At the meeting here, Derek Laney, an organizer for a group called Missourians Organizing for Reform and Empowerment, offered a fine line on the question of how far to go. Yes, they wanted to be peaceful. But still, he suggested, they wanted to rouse the community.

“We’re also committed to having a very determined and a very — I’m choosing my words carefully —yes, militant,” Laney said, “a militant nonviolent direct action.”

He went on: “We want to appear strong and forceful because we believe in what we’re pursuing. But we also definitely want everyone to know we’re committed to nonviolence. We want to disrupt. We want to make the comfortable uncomfortable.”

No doubt, protest leaders here say, there have been conflicts, at times, over leadership, tactics and even over individuals. The St. Louis County Police say they are still investigating a report by a university student who says he was beaten after a strategy meeting last week and questions about whether he was trying to broadcast the events. (Some protest leaders say he was not harmed.)

But leaders here say that is the nature of a movement that has taken place, in part, on social media and that does not match an earlier-era protest structure where a single, outspoken leader might have led the way.

“This is not your momma’s civil rights movement,” said Ashley Yates, a leader of Millennial Activists United. “This is a movement where you have several difference voices, different people. The person in charge is really — the people. But the message from everyone is the same: Stop killing us.”