First, it must not involve wearing a suit. Suits are the uniform for telling lies in, so any occupation that involves wearing them is petty at best, and soul-crushing at worst. Second, it must be okay to leave at five.
Life is too short, and joys too various, to spend more than forty hours a week doing any one thing.
I'm still pondering. Third, I must believe, in some way, however subtle or roundabout, that I'm improving the world. Fourth, there must be something unique and distinguished about the work, and particularly my part of it. There's plenty of money to be made just ripping off other people's well-worn ideas, but I don't want to be the one making it. Fifth, it has to be a job that primarily just involves thinking clearly.