The central principle of all security culture, the point that cannot be emphasized enough, is that people should never be privy to any sensitive information they do not need to know.
The greater the number of people who know something that can put individuals or projects at risk—whether that something be the identity of a person who committed an illegal act, the location of a private meeting, or a plan for future activity—the more chance there is of the knowledge getting into the wrong hands. Sharing such information with people who do not need it does them a disservice as well as the ones it puts at risk: it places them in the uncomfortable situation of being able to mess up other people’s lives with a single misstep. If they are interrogated, for example, they will have something to hide, rather than being able to honestly claim ignorance.
Don’t ask, don’t tell.
Don’t ask others to share confidential information you don’t need to know. Don’t brag about illegal things you or others have done, or mention things that are going to happen or might happen, or even refer to another person’s interest in being involved in such activities. Stay aware whenever you speak; don’t let chance allusions drop out thoughtlessly.
You can say no at any time to anyone about anything.
Don’t answer any questions you don’t want to—not just with police officers, but also with other activists and even close friends: if there’s something you don’t feel safe sharing, don’t. This also means being comfortable with others not answering questions: if there’s a conversation they want to keep to themselves, or they ask you not to be part of a meeting or project, you shouldn’t take this personally—it’s for everyone’s good that they’re free to do so. Likewise, don’t participate in any projects you don’t feel good about, or collaborate with anyone you feel ill at ease with, or ignore your gut feeling in any situation; if something goes wrong and you get into trouble, you don’t want to have any regrets. You’re responsible for not letting anyone talk you into taking risks you’re not ready for.