Are you thinking about cloning yourself or someone else? Well, STOP RIGHT THERE, SIR OR MADAM. The cloning experience is fraught with dangers you may not be aware of, or have forgotten, or are simply too dumb to realize (I don’t know how smart you are). Before you clone anything, read this.
Don’t clone yourself for parts.
It’s not cool. Oh, sure, it’s easy to understand why you’d do it — you’re old and rich and your body is falling apart, and suddenly you think "hey, maybe I need a new liver," and then it’s a short trip to "hey, if I clone myself, I’ll have all the parts I need," and then you’re half-way to thinking “maybe I’ll just move my current brain into a new body!” As The Island — or, the cheap ‘70s movie that it completely ripped-off, Parts: The Clonus Horror — reveals, clones aren’t exactly happy when they discover they're nothing more than a walking container of extra parts. The Clonus Horror takes the steps of making the clones they raise stupid, but eventually one of them is going to escape the compound they’ve been kept in, figure out the elaborate story you’ve told them is a lie, and then freak out. Just stick with buying organs one at a time, man.
Don’t clone yourself to make an army.
Are you a naturally kind and helpful person? Well, then you probably don’t want to take over the world and make everyone bow to your rule. If you’re a power-hungry megalomaniac, it might seem like a good idea to clone yourself to create an army of like-minded minions with your desires and intelligence, because they’ll almost certainly be smarter and more powerful than your current moronic underlings. The problem is that they’re also going to be just as power-mad as you, and end up squabbling with each other or outright trying to kill you to be the new asshole in charge. So many villains have made this mistake, including TMNT’s Krang, Transformers’ Starscream, and Masters of the Universe’s Skeletor. In fact, Skeletor’s tiny clone army of himself was destroyed merely by He-Man asking them, “So, what do you guys get out of it?” Follow Palpatine’s lead from the prequel trilogy, and find some kind of badass without strong ties to the local community to base your army on.
Don’t create a clone for work-related reasons.
Do you hate doing the dishes? I sure do. But do you know why I haven’t cloned myself to make a version of me that will do the dishes so I can go off and play videogames? Because he doesn’t want to do the dishes either. Because he’s me. Why would he possibly want to do the dishes? This is the most eminently foreseeable problem in science fiction, people. Calvin of Calvin and Hobbes pulled this on more than one occasion, as did the Care Bears, and many, many more. And while you might think if you’re normally a go-getter and just need a clone to help share the load, still don’t! Because that clone is going get overworked, have the same idea you will and clone himself, and then that clone will clone himself, and on and on down the line, as in Multiplicity. And that's not even worrying about clone degradation...
Make sure clones can be properly disposed of.
Corollary to the above: Say you have a company with one worker. The company is in a remote location so rather than hire actual employees, you set up an elaborate system based upon a series of clones. The first clone is dethawed, told to work for a three-year “shift,” and when his term is up you put him in a garbage disposal you tell him is a ship back home. This sounds efficient, and it truly is… until one clone gets in a wreck outside, a new clone is dethawed, and he accidentally stumbles upon the last clone, uncovering your whole scheme and freaking out, which is what happens in Moon. The garbage disposal is great, but we all know accidents happen. You need some kind of clone self-destruct. Preferably one that leaves nothing behind but the scent of potpourri. Don't just inject them with a life-threatening virus that will kill them in a few years, such as the bad guy in The 6th Day does, because that gives clones plenty of time to get mad and get even.
Make sure you really want a clone first.
Clones are like tattoos; once you have one, they’re not really going away without some blood spilled and a great deal of hassle. And if you have an elaborate scheme involving creating potentially dozens of clones and then sending them out to live unaware of their nature or each other so you can monitor them and perhaps perform social experiments on them… make sure you really want that before you do it. Because if later on you decide the project is evil and all the clones need to be destroyed, you’re going to have a huge fucking mess on your hands. Case in point: Orphan Black. It might as well be a documentary TV series dedicated to showing what happens when you have a change of heart about your clone experiments.
Don’t make evil clones, period.
Has there ever been a single time that a person has tried to make an evil version of a good guy and had it work out? No. No there has not. I don’t even know why bad guys keep doing it. Sometimes the evil clones have an inferiority complex over their heroic original, and it prevents them from not acting like a ding dong, like Picard’s clone in Star Trek: Nemesis. Sometimes evil also ends up meaning crazy, like Solid Snake’s clone twin Liquid Snake in Metal Gear Solid, or Bizarro (who is occasionally presented as a defective clone of Superman in some, but not all, media). But even when the clone is an exact duplicate, capable, non-crazy and psychologically well adjusted, the original beats them like 99% of the time, such as Luke defeating his clone in Timothy Zahn’s Star Wars Thrawn trilogy, the Tick defeating his (admittedly mucus-based) clone in The Tick, Wonder Woman in JLU, Inspector Gadget, and about a zillion other cartoons and things.
Heck, don’t even clone the good guys.
Honestly, it’s not worth it. The chances of a bad guy kidnapping the clone — probably while they’re young — is about 98%, and then they’re going to turn evil and make everybody’s life hell anyways. When everybody thought baby Cable in X-Men was going to die, they cloned him, and Mr. Sinister instantly grabbed the new baby and turned him into the villain Stryfe. Not getting kidnapped is no guarantee of happiness; X-23 is a female clone of Wolverine and she’s doing all right at the moment, but she spent a disturbing amount of time as an underage prostitute specializing in getting beaten and mutilated, so that’s not cool. Even a guy like Multiple Man, whose mutant power is cloning himself, has problems — one of his clones had a kid and accidentally absorbed it back into himself because it still counted as a clone. In Star Trek: TNG, William Riker’s clone Tom wasn’t a bad guy, but he managed to get into a heap of trouble stealing the Defiant from Deep Space Nine, which is admittedly not nearly as bad as child prostitution, but still. Cloning heroes usually causes at least as many problems as it solves.
Don’t marry evil clones, knock them up, and then abandon them to reunite with the girlfriend she was originally cloned from.
As Scott Summers learned with the whole Madeline Pryor/Jean Grey situation in the X-Men comics, evil clones hate that.
Don’t clone your dead wife and then let her teenaged self hang out with your/her son of the same age without telling either of them they're related.
I feel like this rule should be self-explanatory, and yet Gendo Ikari of Evangelion broke it with predictably terrifying and Freudian results. Because otherwise you are just BEGGING to pay for therapy for the rest of everybody’s life.
Don’t clone yourself for an impressive magic trick, at least if it involves murdering the original.
Not because if you perform three nights a week you have a shit-ton of corpses of yourself on hand, because honestly, in The Prestige, Hugh Jackman manages the body situation quite well. Don’t do it because it’s creepy as hell, man. And really, “I committed suicide hundreds of times for a magic trick” sounds pretty pathetic when you finally say it out loud.
Always remember who’s the original.
You never want to get into a fight with your clone(s) about who came first. Unfortunately, an individual clothing or marking of some kind can be easily replicated, so consider marking the clones, perhaps by numbering them, or even just drawing a prime symbol — ‘ — on their foreheads. In the anime Urusei Yatsura, the clones of Ataru actually all head apostrophes floating above their heads, which was super useful, but hard to replicate. At any rate, if you don’t immediately establish who came first, there is going to be a fight, and the winner becomes the original by default. Special Bonus Tip: Don’t differentiate your clones by adding extra “u’s” in your their names, like “Luuke Skywalker.” It makes them and you sound like an idiot.
Don’t clone Spider-Man.
It’s just not worth it, dude.