When you've got to shoot, shoot -- don't talk!
It's cliche for a villian to do dumb things that will eventually enable the good guys to escape and/or cause the villian's demise.
I stumbled upon this list of "The Top 100 Things I'd Do If I Ever Became An Evil Overlord."
From that list, I've picked my top 25 to help educate you would-be villians out there.
2. My ventilation ducts will be too small to crawl through.
3. My noble half-brother whose throne I usurped will be killed, not kept anonymously imprisoned in a forgotten cell of my dungeon.
5. The artifact which is the source of my power will not be kept on the Mountain of Despair beyond the River of Fire guarded by the Dragons of Eternity. It will be in my safe-deposit box. The same applies to the object which is my one weakness.
7. When I've captured my adversary and he says, "Look, before you kill me, will you at least tell me what this is all about?" I'll say, "No." and shoot him. No, on second thought I'll shoot him then say "No."
11. I will be secure in my superiority. Therefore, I will feel no need to prove it by leaving clues in the form of riddles or leaving my weaker enemies alive to show they pose no threat.
14. The hero is not entitled to a last kiss, a last cigarette, or any other form of last request.
20. Despite its proven stress-relieving effect, I will not indulge in maniacal laughter. When so occupied, it's too easy to miss unexpected developments that a more attentive individual could adjust to accordingly.
25. No matter how well it would perform, I will never construct any sort of machinery which is completely indestructible except for one small and virtually inaccessible vulnerable spot.
28. My pet monster will be kept in a secure cage from which it cannot escape and into which I could not accidentally stumble.
30. All bumbling conjurers, clumsy squires, no-talent bards, and cowardly thieves in the land will be preemptively put to death. My foes will surely give up and abandon their quest if they have no source of comic relief.
33. I won't require high-ranking female members of my organization to wear a stainless-steel bustier. Morale is better with a more casual dress-code. Similarly, outfits made entirely from black leather will be reserved for formal occasions.
42. When I capture the hero, I will make sure I also get his dog, monkey, ferret, or whatever sickeningly cute little animal capable of untying ropes and filching keys happens to follow him around.
43. I will maintain a healthy amount of skepticism when I capture the beautiful rebel and she claims she is attracted to my power and good looks and will gladly betray her companions if I just let her in on my plans.
56. My Legions of Terror will be trained in basic marksmanship. Any who cannot learn to hit a man-sized target at 10 meters will be used for target practice.
58. If it becomes necessary to escape, I will never stop to pose dramatically and toss off a one-liner.
65. If I must have computer systems with publically available terminals, the maps they display of my complex will have a room clearly marked as the Main Control Room. That room will be the Execution Chamber. The actual main control room will be marked as Sewage Overflow Containment.
67. No matter how many shorts we have in the system, my guards will be instructed to treat every surveillance camera malfunction as a full-scale emergency.
70. When my guards split up to search for intruders, they will always travel in groups of at least two. They will be trained so that if one of them disappears mysteriously while on patrol, the other will immediately initiate an alert and call for backup, instead of quizzically peering around a corner.
74. When I create a multimedia presentation of my plan designed so that my five-year-old advisor can easily understand the details, I will not label the disk "Project Overlord" and leave it lying on top of my desk.
75. I will instruct my Legions of Terror to attack the hero en masse, instead of standing around waiting while members break off and attack one or two at a time.
81. If I am fighting with the hero atop a moving platform, have disarmed him, and am about to finish him off and he glances behind me and drops flat, I too will drop flat instead of quizzically turning around to find out what he saw.
83. If I'm eating dinner with the hero, put poison in his goblet, then have to leave the table for any reason, I will order new drinks for both of us instead of trying to decide whether or not to switch with him.
84. I will not have captives of one sex guarded by members of the opposite sex.
87. My vats of hazardous chemicals will be covered when not in use. Also, I will not construct walkways above them.
88. If a group of henchmen fail miserably at a task, I will not berate them for incompetence then send the same group out to try the task again.