So, I made the mistake of asking a random guy for a spot and letting him do a lift off for me. While I've never had any issues with this technique before, this guy clearly had no idea how to liftoff. He pulled it super high and I lost tightness, then he dropped it over my belly instead of my chest, then the bar just dropped and my shoulder made a popping sound and that was it for this workout. This is clearly my fault because I let someone spot me without establishing safety rules.
Now that I'm out with a strained shoulder, I am wondering what is a safety checklist if you're asking for a spot?