Saturday saw thousands of Americans hit the streets for the March for Science to protest President Trump’s proposal to cut billions in funding for scientific research. This mobilization came three months after millions joined in Women’s Marches across the country and separate protests of President Donald Trump’s executive order banning immigrants and refugees from entering the country. More mass demonstrations are in the works.

While these recent protests have channeled opposition to the new president’s campaign rhetoric and first round of executive orders, scholars say it’s critical that today’s protesters learn from history about how protests can succeed — and how they can fail.

“Protests can turn to social movements, but they often fail in an immediate way,” Séamus Power, a psychologist who has done intensive study of austerity protests in Ireland, says. And history is full of examples of protests that fail. The Occupy Wall Street movement sought to highlight growing income inequality in America. It made a lot of noise but didn’t lead to lasting changes. The Arab Spring revolution in Egypt replaced one dictator with another. In the early 2000s, liberals made a noisy plea to end the Iraq War. The war outlived the decade.

“Protest is not enough,” Fabio Rojas, a sociologist at Indiana University, said in an email. Protests can make a lot of noise, but if they don’t influence powerful people making decisions, they fail.

If a protest fails, it can embolden opponents. Occupy Wall Street was “beloved by leftists, but synonymous in the minds of many Americans with disorder, crude behavior, and a message that no one, even its organizers, could explain,” Tom Nichols, a Naval War College professor and author of The Death of Expertise, explains. “Which is why it's not around anymore as a mass movement.”

Protest prioritizes emotion over effectiveness unless *highly* disciplined and targeted. Otherwise, it can play into opponent narrative. /4 — Tom Nichols (@RadioFreeTom) January 29, 2017

So how can protest movements make truly lasting changes? They need to be disciplined, persistent, action-oriented, and focused, experts tell me. Here are four overarching guidelines.

1) Make the message as salient as possible

Predicting the effectiveness of protests is difficult. It’s so hard to directly link the actions of demonstrators to bills getting passed or leaders making changes. “It’s such a chaotic, complex system,” Pamela E. Oliver, a sociologist at the University of Wisconsin, explains. “Imagine a sporting event where there are 12 teams on the field, and they all have their own agendas.” It’s impossible to guess the outcome.

But the research does find a consistent trend: The longer and louder a protest persists, the more likely the government is to take action.

Daniel Q. Gillion, a sociologist at the University of Pennsylvania and author of The Political Power of Protest, has focused his career on figuring out whether a protest can make a real change. “The answer is that it does,” he says.

But it’s not that easy. Conservatives can point to the current mass gatherings and smear them as fringe — unruly mobs of political correctness gone wild. A “protest can embolden politicians to stay the course, and conservative politicians like Trump might be emboldened,” said Gillion.

For a protest to spur change, he finds, it has to become unignorable.

In his studies of decades’ worth of minority activism, Gillion has identified several factors that are key to upping a protest’s salience and, in turn, making real political change.

They include:

Whether the protest lasts longer than a day

If there are more than 100 people involved

If police were present

If political organizations were attached to the protest

If there were arrests, injuries, or reports of property damage

Whether a death occurred

For these more violent categories, Gillion doesn’t make the distinction of whether the violence was incited by the protesters, counterprotesters, or law enforcement. The bigger idea is that reports of “death” or “injury” alone draw attention. “I want to be clear that [violence] leads to increased attention in the way that large crowds lead to attention, in the way that persistence over time leads to attention,” he says.

(And indeed, nonviolence is a winning tactic, especially when the stakes are extremely high. At the University of Denver, political scientist Erica Chenoweth made an analysis of all attempts to overthrow governments from 1900 to 2006 and found that “nonviolent campaigns worldwide were twice as likely to succeed outright as violent insurgency,” as she explains in a TED talk.)

The more salient a protest is, the more likely Congress is to vote on bills that support the demonstrators, Gillion says. “On average, every time a politician becomes informed of 10 protest events happening in their district, they become 1 percent more likely to support a bill that favors a protester’s position.”

2) Unite overlapping protest concerns under one banner

If a new protest springs up every time Trump makes a controversial move, it could mean that each individual protest will get diluted.

If Trump “has more executive orders tomorrow, that are all extreme with regards to women’s rights and the environment [and so on], it could split the coalition,” said Dana Fisher, a sociologist at the University of Maryland studying the ongoing anti-Trump protest movement. “There’s only so much time you have in a day to participate in democracy.”

One solution for dilution, Fisher says, is to form a coalition under one protest. She says the Women’s March did this really effectively. Yes, it was formed to vocalize women’s right concerns. But it also embraced a coalition of people “concerned about a whole suite of progressive issues,” she says

During the Women’s March, she sent out eight researchers to randomly sample demonstrators with a questionnaire. Her preliminary data finds that in addition to supporting women’s issues, 21 percent were there to protest Trump’s attitude toward immigration, 23 percent were concerned with social welfare, and 34.7 percent were there for LGBTQ issues. So there’s a big group of people who want to advocate for the same spate of values. “The question is then how to channel that into meaningful political action,” she says.

3) Pivot from talk to action

“Energy, emotion, and people can certainly make social change,” Fisher says. “But the energy, emotion, and the people have to be channeled into tactics that are effective.”

It’s not enough to just shout in the streets to make social change. This may be especially true of the Trump administration. In the past, Vox’s Dylan Matthews writes, presidents have been responsive to changes in popular opinion. “Which all make it quite disturbing that Donald Trump appears to believe approval ratings are rigged.”

“I think of democracy as a dialogue,” Power, the psychologist, says. “Trump got elected, in part, because certain groups of people felt left behind. And now liberals are responding in the form of protests against Trump’s protectionist policies. It's an ongoing dialogue. … But Trump doesn't listen.”

Protesters shouldn’t expect Trump to relent based on their pickets alone. Instead, they may want to target their messaging and actions to senators who could deny Trump’s Cabinet or Supreme Court appointments. Or they could find ways to generate political or market pressure to get Trump to change his decisions.

During the civil rights movement, Fisher reminds, people didn’t just show up for a march on Washington. They had specific plans of action to put political pressure on politicians to address their concerns. There were boycotts, “freedom rides,” acts of nonviolent resistance, walkouts, and more. Fisher also points to the anti-apartheid movement in the 1980s, where students pressured their universities to divest money from South African companies. Those were specific targets of the protest movement that were thought to move the needle.

The whole goal of a protest movement is to create a political moment that decision-makers — the people in power — just can’t ignore. And protesters need to get creative in how to make that moment.

One criticism of the current spate of protests is that it lacks a leader. But Gillion isn’t sure if an effective protest movement needs a clear leader.

“In some cases, leadership can be detrimental, because people tend to characterize attributes of the protest based on the leader,” he says. “It doesn’t need a leader, but it should have a direction. It should have some grievances that are put out.”

4) Protests can’t just be reactive. They need to be proactive.

Oliver notes that proactive protests — in which demonstrators are trying to prevent an action from happening — tend to be more effective than reactive protests, where people mobilize in response to an outrage. Reactive protests — like the one in response to Trump’s immigration executive order — tend to move the needle incrementally. Arguably, protesters over the weekend put pressure on the White House to clarify whether green card holders are included in the travel ban, for instance.

And the reactive protests made waves in another way: The American Civil Liberties Union, which filed a lawsuit on behalf of immigrants stuck in executive order limbo, received $24.1 million in donations over the weekend. That’s six times the amount it usually gets in an entire year. It’s money to employ more lawyers and take more legal action against Trump’s policies.

A larger, more proactive movement may be necessary to try to get Trump to revoke the ban altogether.

But even if the current protests against Trump are not yet aimed toward specific plans of action or goals, they are doing something important. “The protest is also an opportunity to create what we call ‘collective identity,’” Fisher says. “It’s about getting sympathizers, people who agree with the cause, to be activists.”

If people who are showing up to protests just because they are curious and sympathetic eventually move on to greater, more consistent action, the movement grows. And change can happen.