Thousands gathered in Battery Park to protest Donald Trump's Muslim ban Sunday afternoon. View Full Caption DNAinfo/Gwynne Hogan

Less than 24 hours after President Donald Trump signed an executive order temporarily barring all refugees and travelers from seven Muslim-majority nations from entering the U.S., thousands of demonstrators assembled at JFK Airport Saturday to protest the detainment of several legal immigrants inside.

Thousands more rallied against the ban in Battery Park on Sunday.

Advocates are planning more demonstrations in the coming days to resist an immigration policy they say unfairly targets Muslims and other Trump initiatives.

► Here's Where New Yorkers Are Protesting Trump's Refugee Ban

If you're planning to join the crowd that will urge Chuck Schumer to resist Trump's cabinet picks outside the U.S. Senator's house in Park Slope Tuesday, or the one calling for "No Ban No Wall" at a protest in Foley Square Wednesday, it's natural to have some concerns about your safety.

"There are certainly fears that a lot of folks have with large-scale protests and events," said Michael Sisitzky, a policy counsel in the New York Civil Liberties Union's advocacy department.

But he added that participants exercising their First Amendment right to peacefully assemble and demonstrate their opposition to the president's policies should rely on their common sense and instinct when it comes to protecting themselves.

"If you feel like you're putting yourself in harm's way, just use your judgment in those situations to make sure you're doing what feel safe to you," said Sisitzky.

Here are answers for other common questions and concerns demonstrators may have before hitting the pavement:

What kinds of signs can I bring with me?

The organizers to large-scale protests like the Women's March that happened on Jan. 21 encourage you to bring homemade posters that represent you and your beliefs, but the NYPD won't permit signs affixed to wooden sticks or metal poles, i.e. anything that can be used as a weapon. Be prepared to hold your sign in your hands. Or, Sisitzky said, "If you want to carry a larger sign that's attached to something, we recommend using something like a hollow cardboard tube."

Don't tape your signs to any kind of public property, such as trees, light posts or police barricades. Do that and you'll be violating city posting laws, and could be fined up to $200 for a first offense.

Can I express my political opinions in chalk on the sidewalk?

The NYCLU advises against chalking the sidewalks, Sisitzky said, because the NYPD has been known to arrest individuals caught in the act. That's because the city considers the markings — permanent or not — graffiti on city property.

Can I bring a bullhorn or noisemakers?

Even if the event is permitted by the NYPD to allow for use amplified sound, Sisitzky still recommends you err on the side of caution and leave sound amplification to organizers.

I want to document this event with my phone and/or camera. Is anything off limits?

The First Amendment protects your right to photograph and video-record anything that's plainly visible in public spaces, including public servants like police officers.

But beware: you can be subject to arrest if an officer says your actions impede law enforcement, or "obstruct governmental administration."

"Don't jump in between an officer and someone they're having an interaction with it," Sisitzky advised. "But you absolutely can pull out your phone, take pictures, record and document any activity during the march."

Police have also arrested photographers on the grounds that they're blocking pedestrian traffic, a violation that falls under the heading of "disorderly conduct."

If you feel an officer has wrongly ordered you to stop taking pictures or videos, you can call 311 to file a complaint or submit it to the Civilian Complaint Review Board here.

As for images of private property, private land owners can set their own rules about photography and videography on their premises. If you disobey, they can order you off their property and have you arrested for trespassing.

What should I do if I'm stopped and questioned by the police?

The NYPD can only stop and briefly detain you if they have reasonable suspicion that you have committed, are committing or are about to commit a crime.

"The important things to remember are you have the right to remain silent ... and you can ask the officer if you're being detained or if you're free to leave," Sisitzky said.

The NYCLU also recommends you stay calm and in control of your words, keep your hands visible, and never "bad-mouth" an officer, run away, or otherwise resist.

You're not required to carry identification in New York, and you don't have to show your ID to a police officer. But, keep in mind: if you refuse to reveal your identity when an officer issues you a summons or arrests you, he may detain you until you can be identified.

If an officer takes you into custody, stay silent and request a lawyer, Sisitzky said. "Ask for a lawyer if you've been arrested, tell them what happened, and if you want to take actions later on to hold the officer accountable, you can reach out to the Civilian Complaint Review Board, you can dial 311... and you can also reach out to the NYCLU."

Can I be fired for participating in a political protest?

New York state's labor code prohibits employers from firing employees for political activities they pursue in their free time, outside the office and without use of company equipment or property.