The golden rule is never click links. You can preview them first on any link shortener previewer. Just bookmark them for easier access.
Use Tor or VPN, or both. A VPN whose main address is not in the United States or not an NSA friendly country. And make sure to download Tor from their main website.
Which VPN Services Keep You Anonymous in 2017? https://torrentfreak.com/vpn-services-anonymous-review-2017-170304/
If anything asks for a phone number (you should avoid the service if possible if they ask for one), use burner phones or public phones in coffee shops or such. Buy the burner phones at any store and pay CASH.
Never use your real email address in anything you want kept private. People actually put their REAL NAMES on their twitter email addys! The email address I have on my twitter is only used for twitter. And don't have email addys the same as twitter addys because it would be easy to guess an email address to hack. For example:
Twitter addy - @JohnSmith
Email addy - JohnSmith @ whichever email service you use
Do not do the above because they will guess what the email address is. Add numbers or extra words to the email addy such as JohnSmith2017OMGlulz@ whichever email service.
Keep your mouth shut about your personal info. So many people tweet all their info and pictures.
Change your timezone in all your accounts to trick people. They can tell on twitter accounts and services twitter users use.
If sharing info instead DMs which are not encrypted and twitter group accounts can see, use Privnote. You can set it up to expire once it's been read. https://privnote.com/
There's Tor Messenger that encrypts twitter DMs. It's still in Beta. I "think" encrypting DMs also works on group DM too. Not sure if it does group dms yet.
Any downloads should be done directly from Tor's website, which include phone apps. There are phony apps. https://www.torproject.org/download/download.html.en
Keep all devices and browsers updated.
Don't add any addons to Tor. You have to look like everyone else.
A good private chat room for groups seems to be https://www.chatcrypt.com/. Barrett Brown's new project is working on a secure chat service but it's still very new and Beta.
Don't tweet personal pictures of yourself because they can do an image reverse search which will show in many cases who the person is if the picture has been placed anywhere else online. They don't index all pictures but a good deal of them.
Here's a great guide for many privacy services.
Tips, Tools and How-tos for Safer Online Communications
Digital Security Tips for Protesters https://www.eff.org/deeplinks/2016/11/digital-security-tips-for-protesters
Attending Protests (United States)
Attending Protests (International)