This is number 1 in Yale History Professor, Timothy Snyder’s, Fighting authoritarianism: 20 lessons from the 20th century. I discovered this great list via Kottke.org, read it in full there.
1. Do not obey in advance. Much of the power of authoritarianism is freely given. In times like these, individuals think ahead about what a more repressive government will want, and then start to do it without being asked. You’ve already done this, haven’t you? Stop. Anticipatory obedience teaches authorities what is possible and accelerates unfreedom.