In the new science-fiction comedy The Watch, it’s up to a newly formed neighborhood protection group (represented by Ben Stiller, Vince Vaughan, Jonah Hill, and Richard Ayoade) to fight off an alien invasion. While the Earth intruders may have superior firepower and defenses, it shouldn’t be too difficult to do since they have one hidden weakness: As Vince Vaughan soon discovers, “You can only kill these guys if you shoot them in the dick.”

As the movies have taught us again and again, firing aimlessly at extraterrestrials won’t do the trick—the secret is to discover that even Martians and little green men have their own Achilles’ heels. Thus, having consulted the tapes and scouted out the opposition, we give you a guide to vanquishing the alien invaders who appear indestructible … but are truly not.