OK, here's one that proves foolproof for me, but you're going to laugh...

There are so many steps in making a large format photograph, from leveling the camera on the tripod to putting the dark slide back in the right way, that I go through them verbally, out loud, every single time I make a photograph. Even if I am making a portrait. Especially when I am making a portrait.

I have ruined so many photographs by the stupidest things, like shutters not closed or slides not pulled or slides put back in white side up. And when I photograph people, I am so focused on the person that I tend to make the most mistakes.

So there's a rythm I found years ago, and I stick to it invariably.