I will never, under any circumstances, reveal information to any of my enemies that could be used against me.
On a regular basis, my guards and staff will interact socially, that way when someone shows up and claims to be the new guy, my guards can answer "I didn't see you at the 8 o'clock meeting" and shoot the intruder.
If I ever have a child, I will keep them as happy as possible, as an unloved child would likely betray me and defect to my enemies. I will also groom them to be the next overlord, and let them choose their spouse.
I should try to keep unemployment to a minimum. Keeping my subjects impoverished is fine, but if they have no jobs, they'll be more likely to revolt and assist the heroes.
I will offer unemployed people work as soldiers in my armed forces. If they refuse, I will remind myself that I'm evil and have no use for bums on welfare, and arrange for them to find "employment" elsewhere.
I shall also remember to give these plans just enough security that the hero never says "This is too easy."
Whenever I take over another country, I won't force them to give up their culture and follow mine. Instead, I'll simply introduce my customs and they will catch on soon enough.
I will keep all my underlings well paid and give them good working conditions to avoid disgruntled workers being led by the hero into a rebellion. This will include a dental plan.
I will remember that any enemy soldiers that are not the Hero or in his company are incapable of reliably capturing or killing me. Therefore, I will face an entire army instead of facing the Hero if I am given the alternatives.
I will know that the best defense is the status quo, so I will use it against the hero and do everything in my power to maintain it.
Regular appointments with my psychiatrist will be scheduled. Split personalities and other forms of mental illness can lead to my downfall.
Any potential lieutenants must also pay my psychiatrist an annual visit. Anyone diagnosed with disorders that might interfere with their duties will not be promoted. Anyone diagnosed with megalomania or the like will be shot before they try to overthrow me.
I will not drink. It impairs judgment. Or do drugs. It's only useful to pretend to be high. Anything else gives the hero an opportunity to shoot me.
If my guards are equipped with poison, it shall be a mixture of no less than 18 different samples that cannot cancel each other out. Also, said poison will only be applied to bullets, not put in a bottle or syringe that is carried.
My Legions of Doom will also be instructed to carry the antidotes to any poisons they use in a securely locked container. I don't want the heroes curing the poisoning by just beating my minions.
I will not make my organization a serve-or-die type. If that happens, people get resentful and help the Hero. If they wish to leave, they may, if they don't say a word about it. However, it will be made clear that should they violate the non-disclosure agreement, their lives are forfeit.
If I ever decide to have dinner with the hero, I will not attempt to poison him through the food. There are far too many things that could go wrong. Instead, I will rig the room with lethal booby-traps. Or even something simple like a poisoned tack under the hero's seat. Not such a childish prank now, is it?
My prison will be as far away from my primary base as physically possible. The base will have cells for temporary confinement, but all prisoners will be transferred to the main prison as quickly as possible. Their equipment will be sent to a different facility even further away.
I will not rape anyone, ever. Doing so is a one-way ticket to a karmic death, and those are never pleasant. Besides, if I want to be a competent overlord, I have to be able to control my primal urges.
If I have a wife or girlfriend, I will remain faithful. The wrath of a royally pissed woman is one of the most powerful forces in the universe, and I'd rather not face it. I'm not having my plans shot to hell because I couldn't keep my pants on.
If my marriage does go sour, I'll do my best to end it amicably and leave my wife with a decent alimony, to make her less tempted to help the hero. Or just quietly kill her.
My plans will not involve animals when it is not really necessary. I will not drop the hero into a snake pit when a pit of poison-coated spikes will be just as effective, and a lot cheaper.
Despite how cool it would be, I may have to refrain from creating weird hybrid animals, as it would be incredibly expensive.
If I have hypnotic or mind control powers, I will keep my weapon ready just in case my control is broken.
I will not disregard any potential threat simply because it's just a kid, as they may turn out to become a kid hero.
Anyone who poses a threat to me will be quietly unpersoned, and their disappearance will be blamed on the rebels.
If I am ever face-to-face with the protagonist, I will only give my villainous speech to him/her when they're disabled or killed.
My guards will be specially bred to remove their sexual inclinations, thus closing the loophole provided by Rule #84 that seems to be under the impression that gay guards don't exist.
I could just use robot guards, of course. But make sure that the robots are actually robots, and don't dream. And I'll make sure they can't be reprogrammed without retinal clearance from my top roboticist, my head of security, and myself.
I will have the retinal scanner disguised as a finger-print scanner. If anyone puts, say, the severed hand of my head of security up against it, it will spectacularly explode.
My scientists will put in the extra time to proof any mind control devices against love or friendship.
I will store the plot coupons in a single place. The door that needs the coupons to open will be between the hero's starting location and myself. Ha.
If I develop a superweapon to use against the heroes, its first public use will be against the heroes. Any tests will be made in out-of-the-way locations against people that will never be missed, so the heroes will have no warning and no chance to develop a counter-measure.
I will never depend on superweapon plans that were posted on the Internet.
I will take anger management courses. That way, when the hero taunts me and runs, I will not become enraged and blindly chase him right into a trap.
I will design my computer password system so that the third failed attempt to log in will route the user to an apparently legitimate database full of misinformation. Then I can laugh quietly at them as their entire organization prepares to counter my non-existent schemes in Antarctica.
If I ever need to protect something vitally important behind an array of magical defenses, I will try and incorporate at least one which uses a password or other means of identity verification. Whilst ancient riddles and tests of skill will keep the riff-raff out, they also grant entry to anyone capable of working them out - and heroes tend to be annoyingly good at this.
However in a fantasy or science fiction setting, I will always consider the possibility that death is not permanent.
If I must team up with the hero against a greater villain, I won't immediately and impulsively betray the hero after defeating our common enemy. I will patiently wait for a more convenient time to double-cross the good guys.
If I must team up with another villain against a greater enemy, I will keep my guard up. When working alongside a similarly despicable person, there's a good chance that they'll plan to back-stab me. I may have to back-stab them first.
I will not, under any circumstances, trust some upstart new villain that I've never met; especially when they suggest a plan to take down the heroes that I've never thought of, or that requires finding some new weapon that they guarantee will help defeat the heroes. This plan will inevitably elevate the new guy at my expense.
I will use heroes by informing and directing them to my enemies that are more (overtly) evil than I am. Heroes tend to ignore lesser evils when a much larger one looms over them.
On top of never gloating, I shall never so much as talk in battle. It's a distraction and any moment I could spend thinking of something to say, I could instead be using to predict my opponent's next move and a respective counter. Cold silence is intimidating as well.
If I am ever short on cash but have a handy new invention, and I have the choice between using this invention to steal money in a heist that will bring me into direct confrontation with the hero, and just selling it on eBay for tons of cash and collecting anonymously, I will choose the latter.
I will not only allow but encourage my Legions of Evil to paint unique designs on their armor. Not only is it a slight morale booster, but it also makes it easier to identify individual soldiers and thus makes it that much harder for the Hero to impersonate them.
If I absolutely MUST use a slow death trap for an execution, I will use it on a hero first. I will not put a nameless redshirt in first, allowing the hero to figure it out. Nor will I put the hero's love interest in the death trap first, as this inevitably leads to a last minute rescue.
If I'm having audio-only contact with one of my minions, and the connection is suddenly broken, I will treat the situation like a full-scale emergency. It doesn't matter if contact is reestablished right afterwards and a voice assures me that everything is all right and that it was just a minor glitch; I will nevertheless assume that there's now an enemy at the other end of the line.
I will not keep a gigantic, man-eating beast that is likely to eat just about anyone who happens to be dumped into its moat or dungeon. If it can't be trained into never trying to eat me, it's not worth the risk.
When a noble hero convinces another, less noble hero not to kill me, it is not the right time for me to push my luck. In a situation like that, I will not mock them for being so naive and promise that eventually I'll kill them both. Instead, I will act humble and remorseful for as long as they've got me dead to rights.
I will not suddenly start acting evil again once they've no longer got me, either. I will at least wait until they're out of both sight and earshot.
If I hear a suspicious sound coming from somewhere in my fortress or just outside my camp, I will send out three henchmen to investigate: one in the direction from which the sound was coming, two in the opposite direction.
If I do not get updated on the situation within a reasonable timeframe, I will have the area under heavy guard, with powerful weapons prepared in case of sudden hero encounters.
I will build more hospitals. The doctors and medics will treat soldiers first, and civilians second. This means I'll lose less soldiers, civilians will have more incentive to join my forces, and my subjects will be far more loyal. It isn't evil in nature, but it allows me to further my evil cause(s) more easily.
I will make the first Friday of every month "Funny Hat Day". Not only will it raise morale of my Legions of Evil but the hero will think twice about posing as one of them when they have to wear a hat made out of fake fruit.
I will not hire a busty bombshell as my second in command. They may be aesthetically pleasing, but I shouldn't be choosing someone based solely on appearance rather than merit.
The borders of my realm will be well guarded with checkpoints and preferably a 50+ feet high wall with motion sensors. Said sensors will be linked to a number of machine guns. Any outage in the motion sensor grid will be treated as an emergency.
Incentives will be offered should someone find a legitimate flaw in the security system, be it from a minion or civilian.
Should the hero somehow enter my realm, I will NOT allow him and his party to carry on while I plot his demise. He shall instead be greeted by an airstrike.
I will find alternate means of dealing with any enemy who would become more powerful if killed.
I will make certain that my squad of superpowered evil minions aren't particularly weak to each others' powers. While this can be useful in containing rebellion, there are many power-assimilating heroes out there. Alternately, I will pair each minion with the counterpart that strengthens/heals them.
If the super-empowering substance I possess has a possibility of horrible side effects, I will neither force a minion to take it, nor try it myself. I will instead wait for version 2.0.
As an alternative to Rule #167, I will hire both the programmer and the kid and make sure that they work as a team. Not only will their combined ideas increase my computer systems' security, but the hero will have to man the keyboard himself.
I will hire a complete lunatic as one of my advisers, but the first idea that he has to defeat any of my enemies will be treated as a last resort. If unsuccessful, he will be dealt with in a manner that will ensure that he can never help the hero (even by accident) in any way.
An alternative to Rule #2: I will keep the air vents large, because crawling through there makes a lot of noise; so when the hero tries to escape, I can just have my men shoot at the sound. Also realistically, the air ducts will simply break under his weight, providing amusement as he tries to spy on my plans.
Another alternative to Rule #2: I will keep the insides of my air vents at lethal temperature extremes. This function will only be disabled when they must be repaired (and I will check the identity of the repairman).
My motives will always appear to be sympathetic. The reason is simple; if the hero thinks that I'm just misguided, they'll try to talk me out of whatever I'm doing, instead of constantly trying to kill me.
I must never underestimate any hero. I will always assume they're a threat, even if they're stupid/silly/naive/dead. And I will expect my underlings to assume the same.