@kissane That was a great read.
I absolutely love your very obvious, and horribly overlooked, suggestions:
Test it - thoroughly.
Document it - throughly.
Those 2 points are so critical to the success of anything technical, and yet, they are often times done poorly or not at all. I get that writing documentation is not glamorous and is time intensive, and those alone turn off a lot of people from writing documentation, but it needs to exist.
One thing I've adapted when writing technical instructions: write it as non-technical form as you can. That helps to ensure the greatest chance of success.