(A big thank-you to sandylikeabeach, who reminded me that zombies indeed really truly do exist . . . get your shotguns ready.)
How to Make a Zombie
First, get a victim. Also, you have to be a voodoo priest. Assuming you have both, next you mix your zombification drugs, like tetrodotoxin, a nerve poison that comes from the puffer fish and is deadlier than cyanide. Interesting side-effect: it produces paralysis and a death-mimicking state, which is what you, as a zombie priest, want.
After your victim is zombified, and presumably buried (I suppose embalming is not something usually done in Haiti, but don’t try this in Ohio, because they definitely embalm–sorry Steve, I really didn’t know–and that zombie powder is not cheap to export and I should shut up now), you dig him up–with the help of your legion of already-made zombie slaves, of course–and administer the next step in the process: a mind-controlling drug made from the plant Datura stramonium. You may also have to rely on some additional ancient voodoo sorcery.
But mostly, drugs.
So, thusly: zombie powder + dude you don’t like + premature burial + mind control = zombie
How to Keep a Zombie
Don’t feed them salt. Seriously. In 1918, Ti Joseph, a voodoo priest working for the American Sugar Corporation, fed his zombie gang only unsalted porridge. Feeding your zombie salt will cause him to freak the fuck out, resulting in the zombie attempting to return to his grave.
I don’t know. I read an account of zombies going haywire after eating salted peanuts in Reader’s Digest Mysteries of the Unexplained when I was a kid, and it’s stuck with me. I suppose the salt counteracts some of the zombifying potion or something.
Otherwise, a zombie makes a great laborer/pet. They don’t decay, like movie zombies, and they can’t think or speak very well, due to the plant drug and a side-effect of the puffer fish toxin, which affects the left side of the brain, the side responsible for speech and memory.
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For more zombieness, you can read Wade Davis, a Harvard ethnobotanist, who wrote The Serpent and the Rainbow (1985) and Passage of Darkness: The Ethnobiology of the Haitian Zombie (1988). If you don’t feel like wading through books, Wes Craven made The Serpent and the Rainbow into a movie in 1988.