I'll put my keys on top of my lunch in the fridge, because then I can't leave without remembering my lunch.

The problem comes when I am going out of my mind looking for my keys, screaming that I'm going to be late, until I finally remember that I made lunch, and the keys are with it.

Your technique is my technique. For things that can't wait by the door, I use whatever object will jog my memory. Fork for lunch, helmet for bike, charging cable for devices, etc.