If you are unsure about what exactly can cause you to end up on the no-fly list, there's an article on the subject here with links to the official government document. If you just want to read a pithy summary of the problems, one is here.
Of course, that's the standard for when the President is trying to get Islamic terrorists to stay off airplanes. Once the power expands to keeping his political enemies unarmed, I assume that an already-terrible standard will become unimaginably worse.
Also, you have to give up your data to the State. For security. As someone whose every secret was hacked in the OPM data theft, I find that hilarious. But of course, it's not my security they care about.