To tell whether the monster about to kill you is a zombie requires some knowledge about other undead monsters.  If the entity is just behind the door, you may wish to arm yourself before completing this article, just in case.

There are, to date, five best known undead entities that we need to consider. Technically, not all undead are even monsters.  Still, if you are killing in self defense, it will not matter.  We will examine the following five: Vampires, Ghosts, Mummies, Cosmic beings, and lastly, Zombies.

Right now vampires are especially popular, they are easy to distinguish from zombies as they look attractive, debonair, and are usually very well dressed.  Vampires cast no reflection, and modern vampires sparkle in sunlight, whereas old-fashioned vampires used to sizzle, and burn much as gingers (red haired people), but much more quickly.

Vampires are very much night owls, although their totem animals is bats. They wear black, feast on negative energy, sleep during the day, and although living, seem obsessed with darkness and death.  For these reasons, they are often confused with teenagers.

The easiest way to know whether the entity in your home is a teen or a vampire is to ask. If the entity speaks a foreign language, or is unresponsive, it is probably your own kid.

Vampires feast on human blood, and unlike teens, they will work hard to get it. The only way to kill them is with a wooden stake through the heart.

Ghosts come in several varieties.  Most ghosts do not have any wish to harm anyone. They are stuck between worlds, and just groan, weep, wail, thump and bang because they are weary of waiting for closure.  If you have ever waited in line at the DMV, or other government agency, you understand how all the tapping and fidgeting occurs. When they do haunt homes, it is usually because whiny and tedious people there jump every time a door creaks and impatient ghosts are fed up.

Mummies are long dead preserved humans that, like ghosts, seldom pose any threat. They shuffle, are slow, are fairly sightless and deaf, (usually having their eyes and brains stuffed somewhere else in fancy jars) and easy to detect because of their wrappings.

They are usually tied to some bizarre cult or outdated religious belief system like televangelists, or Catholicism.  Mummies often are known to be kept in museums, and exhibits.  Others, like rock stars, are often on tour.  This is because they were very popular in life.  Also, they are usually very old, any may be somewhat decrepit, like The Rolling Stones.  Some experts even ascribe to the idea that beneath all the wrappings and shrouding, there is no body at all. Simply pulling at the bandages can unravel the mystery.

Other undead beings are cosmic beings. These include Jesus and his whole family, some saints, Elvis, and some prophets. Those cosmic undead which are still very popular visit in manifestations on toast, rock formations, billboards, and occasional marketing advertisements.  Most cosmic beings are at best, benevolent, and at worst, inept, so not to worry.  They can easily be discerned from zombies because they have little to no interest in brains. They are after souls.  

As to what has become of some cosmic beings which were quite popular once, and now seem to have disappeared there is uncertainty what category of being they are among. Zeus, Lilith, Madonna, Snoopy and Garfield, and John McCain seem to have melted off into the murky shadows of these marginal beings.

Zombies, who are undead on a mission to eat human brains, can be detected by sight, smell, motion, and behavior. All of these aspects are poor in zombies.  They can be killed by either smashing the head, decapitation, and some say salt in the mouth.  If you have any doubts use one half cup of salt, and a swift decapitation swing of a crowbar, bat, assault rifle, or what ever object is at hand.  Styling wands and smart phones are usually ineffective, for example, but if it is the only tool available, by all means try it.

2012 is prophetically assigned to be a meaningful year for zombies, as the coming Zombie apocalypse, and the overlapping regular apocalypse, is expected to unfold. Also in this banner year, election hype, and lots of brainlessness will be exhibited on every network, and in all babble of society, so zombies are expected to become wide ranging in search of brains anywhere they can find any.  To avoid being a victim, stock up on books and retire to a concrete bunker.