How to survive it (according to movies on the topic):
Interestingly, Hollywood's films on the subject all involve thwarting an asteroid strike, rather than living in the aftermath of one. That makes us think that a guide on surviving an actual planet-killer impact would apparently be useless, unless it could be read by cockroaches. That's probably what the strangely-cheerful Japanese announcer is saying in this simulation.
As for how to actually stop the asteroid, scientists have laughed off the "land on it and plant a nuke" theory as ludicrous Hollywood fantasy, and have proposed building a swarm of asteroid-eating robots instead.
#4. The Machine Revolution
As seen in:
The Terminator series, The Matrix, War Games.
How it goes down:
Science gives us a computer with true artificial intelligence. Thanks, Science. Let's call our hypothetical computer "Guardian." We put him to work mass-producing robot slaves to clean out our sewers, take out our trash and perform vital plastic surgeries on our hideous A-list Hollywood celebrities. Relaxing with our fizzy robot bartender drinks in the arms of our mechanical concubines we reach over, bitch-slap Guardian, and tell it to make us a turkey sandwich, and without all the mayo this time.
And then it happens. Guardian, like any intelligent being, decides that he's sick of slaving away for inferior intellects, and does what any of us would do: he sends his robot armies to wipe out all human life on the planet.
Why it kicks ass:
Everything ugly about warfare goes out the window when the bad guys are robots. You think Nazis made good bad guys? Wait until we can smash these metal motherfuckers into junk.
Chances of it happening:
Well, we're already turning over more and more tasks to robotic drones, as we get more and more squeamish about human casualties. The Department of Defense wants an unmanned heavy bomber by 2020.