From his Mixergy interview (4/30/10) [1]:

``I have a physical checklist for when I’m doing a deployment. It’s, off the top of my head maybe six commands long; one, two, three, four, five, six. I check them off; dink, dink, dink, dink, dink. And then after I do that, I have the other checklist to verify that it actually took, you know the things that I did that had the expected effect. I missed doing that once because I was exhausted at the day job and, sure enough, that was my biggest down time in four years. So I’m trying to be better at it in the future.''

[1] http://mixergy.com/patrick-mckenzie-interview/