Open source builders: what actually makes you click 'Star' on a project?

I've starred probably two hundred repos and I honestly couldn't tell you my own criteria. So I'm trying to reverse-engineer it, because I'm about to open source something and I want to understand what actually earns a star versus what just gets a polite look.

My suspicion is that it's rarely the code. It's usually one of three things: the README answers my exact question in the first screen, the demo shows the thing working in under a minute, or I saw the maintainer answer a hard issue thoughtfully and decided the project was alive.

The third one is the one I think people underestimate. A star is often a bet that the project will still be maintained in a year.

So: what actually made you star the last repo you starred and have you ever un-starred something? If so, why?