As a thought exercise i suppose one of the first act of resistance would be the sabotage of the military equipment in the hands of non-military organizations such as the DHS, TSA, city police departments, etc.
Easily done to most small departments, poorly protected. Some of this stuff is out in the open near city streets. I've wondered, just how would the rebellion start? A few cells laying siege to federal buildings, or raids on police stations? Whatever happens, it would be quick and the culprits would quickly disappear to strike elsewhere. Lots of small operations simultaneously everywhere to throw the tyrannicals off balance.