Up until yesterday, it had been a month since I'd flown. My 90-day solo sign-off had expired, so I needed to up with an instructor before I could do pattern work. The guy I've been learning from is gone on vacation for the weekend, so he arranged for another instructor to come fly with me a sign off on solo flight.
This new instructor wanted to check out what I knew, and he's a very detail oriented person, so he ended up quizzing me in the airplane about a bunch of stuff. He asked me multiple times "what do we need to fly?". He wanted me to be able to execute procedures without looking at the physical checklist, which is different than I'm used to doing it. He made the point that you should do the check list without the printed list, then check the list to make sure you'd done everything.
After a very long discussion, I started the engine, and then he went over some other things while the engine was idling. About two minutes in, the engine stopped. I said "that's wierd; that's never happened before.". The first thing I checked was the fuel shut-off valve--it was OFF. He'd turned it off at some point, after my pre-flight (where I checked that it was ON) but before I got in.
I was very angry and annoyed at the time, but on the drive home from the airport, I decided that the point of the lesson was that I needed to be able to do the important checklists without reading them. Some of those operations I may need to do in a hurry, or with lots of other things going on, and it may be that I won't have the luxury of being able to pull out the written list and check it.
I am now also incredibly paranoid about fuel shut-offs. :-) Which I suppose is a good thing.