This is a 71 page handbook with detailed operational security advice for activists.
This is a very old guide from the Office of Strategic Services (OSS)--America's World War II-era predecessor to the modern Central Intelligence Agency (CIA). The manual describes how activists in occupied countries can sabotage the enemy war effort.
It is also important to learn these methods to make sure that they are not being used against you.
This is a Wikipedia page that explains the methods use by protesters in Hong Kong to oppose their local police force and Chinese influence.
This is a blog post by the well-known security expert @thegrugq. In the post, he details a strategy for running a completely pseudonymous Twitter account.
He recommends the use of a now-defunct email service called SIGAINT. Today's activists should use ProtonMail instead.