I have a checklist in my head, but to make sure it works 100%, I always make two trips around - and if I find anything that has to be fixed, I fix it, then start the checklist over from the top.
I start from the same corner of the vehicle every time. Check things in the same order every time.
One time I completed my check list. Twice around. Start up. Pulled out. Headed on down the highway. But something sounded wrong. So I took and carefully listened to each sound.
Little bit of a whistle of the air going around and over the cab. Normal.
Even running sound of the engine. Normal.
Rhythmic bumping sound of the tires crossing the expansion joints in the highway. Normal.
It was wrong.
It was too quiet.
Something was missing.
Wait.
No one told me I was turning the wrong direction at every intersection.
Crap.
I forgot she was going to the dumpster to get rid of the trash.