I'd add a rule 6 for the stubborn (like me).
6: If it is too cold, and too late, and you are getting frustrated, STOP. A frustrated mechanic is worse than a drunk mechanic, and you may make drastic decisions (like dropping your tranny to retrieve a dropped wrench), or stripping out a difficult to access bolt (ask me how I know). Better to throw your tools in the trunk, and go inside for a while, the car will still be there when you calm down.
peace,
sam