Well, this example was off the top of my hat, and just an illustration rather than a realistic example.
I agree with what has been said regarding that checklist. However, improvisation is something you must practise in order to get better - it's not just a talent. I thionk it's a nice list to fall back on, lest you should draw a total blank in game. Over time, I think the steps will actually merge into one: go with it.
However, when a player asks me whether his spectral stag manages to throw the villain over the railing, I must consider several options by default. There's no problem in thinking about their effects, as well.
the rail could hold, but that would not please any player, not be especially cool. The railing could break, but the villain has a fly spell ready. The rail breaks, and the villain topples down to the ground, taking damage. These options come to my mind naturally, and it's not bad to chosóse the cool one, or the gratifying one over the boring one.
It's also a nicce way to just make you think about your decisions, and not just nodding to everything the players do, or declining every option.
And last but not least, anyone who has ever done improvisational theatre knows that indeed, improvisation follows its own rules and chematics as well. Coming up with something on the fly must not be a totally chaotic endeavour.
