I don't agree with all the particulars in this essay (for example, I prefer Wire or Riot.im to Signal), but it's an excellent summary of good privacy / security practices.
"If you post publicly on social media, know that local police (and likely federal agencies as well) keep tabs on activists online. For example, Facebook, Instagram, and Twitter have all fed data to social media monitoring products that police departments used to track Black Lives Matter activists.
Even if you keep your privacy settings on lockdown, social media companies are subject to subpoenas, court orders, and data requests for your information. And often times, they’ll fork over the information without ever notifying the user that it’s happening. For the purposes of social media, assume that everything you post is public. This doesn’t mean you should stop using social media, it just means you have to be mindful of how you use it.
If you’re an activist, consider using a pseudonym for your activism. If you post online at all, take others’ safety and privacy into consideration as well.
Who are you tagging into your posts? Are you adding location information? Who are you taking a picture of, and why? Be particularly careful with photos or posts about protests, rallies, or meetings. Facial recognition technology is fairly sophisticated now, so even if you leave people untagged, theoretically an algorithm could scan for and identify activists in a photograph of a rally. You can already see this at work in Facebook’s tag suggestions."
https://motherboard.vice.com/en_us/article/a37m4g/the-motherboard-guide-to-avoiding-state-surveillance-privacy-guide
"If you post publicly on social media, know that local police (and likely federal agencies as well) keep tabs on activists online. For example, Facebook, Instagram, and Twitter have all fed data to social media monitoring products that police departments used to track Black Lives Matter activists.
Even if you keep your privacy settings on lockdown, social media companies are subject to subpoenas, court orders, and data requests for your information. And often times, they’ll fork over the information without ever notifying the user that it’s happening. For the purposes of social media, assume that everything you post is public. This doesn’t mean you should stop using social media, it just means you have to be mindful of how you use it.
If you’re an activist, consider using a pseudonym for your activism. If you post online at all, take others’ safety and privacy into consideration as well.
Who are you tagging into your posts? Are you adding location information? Who are you taking a picture of, and why? Be particularly careful with photos or posts about protests, rallies, or meetings. Facial recognition technology is fairly sophisticated now, so even if you leave people untagged, theoretically an algorithm could scan for and identify activists in a photograph of a rally. You can already see this at work in Facebook’s tag suggestions."
https://motherboard.vice.com/en_us/article/a37m4g/the-motherboard-guide-to-avoiding-state-surveillance-privacy-guide