Do not misdiagnose an electrical fire as an engine fire, shut down the engine unnecessarily, crash into houses, and die. As has happened.
Which accident report was the first thing that leapt to my mind once when I smelled burning on the climb out.
So I did nothing at all. Except think about it. For a long long loooong time - whole seconds, and then more whole seconds.
Then I turned off the cabin heat and the burning smell went away. I had eventually managed to work that it must have been the first time that autumn anyone had put the cabin heat on, so there was some dust burning off.
Now, that sounds like a trivial story, but it isn't. If I'd thought "engine fire" and shut down the engine I probably wouldn't be here now (there aren't many places to go off 23 at Cambridge).
And I don't recall seeing that one in an emergency procedures checklist. Which may, of course, be because I haven't read one recently and have forgotten it.