Don’t forget to walk out on stage.

Don’t forget which agencies you would abolish.

Don’t talk about killing a man.

These are all things you should avoid if you are trying to convince the American public you are presidential material. They are also all things that presidential contenders have done in debates.

Democratic 2020 candidates are prepping right now for this week’s debates, brushing up on policies, practicing their game faces, sharpening witty comebacks.

All good.

But for a primer on what not to do, we present this compendium of debate disasters as a public service.