When you have the option, make it a habit to be an open book. Freely reveal important information to advance your cause and fight against the misinformation that others may be disseminating.
When you’re transparent, you build trust and you become a source that people can rely on. This doesn't mean you need to be 100% transparent in all cases. Often, you have the option of various levels of transparency, and it's up to you to sense how much transparency is warranted in any given situation.
It's often said that people who are guilty try to hide things. That's not an absolute, but it can be a red flag, which is why you should make every effort to let people know as much as possible without compromising your efforts.
When you choose transparency, you may be attacked for what you reveal. But as long as your cause is just and you tell the truth, that's the other side's problem and not yours.