There are leaders, and then there are masters. You've got the archetypal Master in Doctor Who, but masters include anybody in a black cape whose minions say "yesssss, master." How can you get some master action? Let us show you.
1. Experience a horrific trauma or terrible setback that fills you with power lust and an unhealthy desire for revenge. Really, it could be anything. Did somebody tell you that mega-knights weren't supposed to have sex with princesses even though princesses are totally hot? Did somebody unfairly lock you in a burning, underground chamber or two-dimensional space square just because you tried to rule the Earth? Do you just want a special companion who will understand your urge to convert animals into humans, but THEY keep thwarting your every move? All of these are legitimate sources of trauma and anger, and will be perfect emotional springboards from which to launch your reign of terror.
2. Try to do something sort of good, but discover that goodness is weakness. Give some frozen yogurt to your object of affection while explaining your plans to subjugate the continent. Oops - that drove her into the arms of your arch nemesis. Attempt to improve the planet by unleashing everyone's "true selves" via drugs in the water. Why are people so ungrateful? You are just giving them what they want! Save a cat who bites you. Yet another ungrateful creature on this planet! You'll show them!
3. Pick an outfit that says "master." Obviously black is a good way to go, especially if it's shiny, has a lot of laces and buckles, and is topped off with a flowy cape. Latex is a must, at least somewhere. Masks are also good, especially if they distort your voice, but helmets cannot be underestimated. Bonus points if your outfit conceals, but also calls attention to, some disfiguring injury that you suffered while doing evil or being traumatized into your life of evil.
4. If you would like to be a mistress, make sure your outfit is dangerously sexy. Men can be mistresses who want to build the ultimate man and control time itself, but they still have to wear corsets and high heels. In general, a mistress outfit should be skintight, possibly garnished with feathers, sequins, spikes, or inexplicable epaulets. A high collar attached to a short, kicky cape is also a good idea. Headgear should be at least as large as your head.
5. Get a submissive sidekick to call you master. Mind-controlled beefcake, robots, and deformed creatures with horns make great sidekicks. You should always have one chief sidekick who rules the minions (for more on minions, see below). Do not despair if you can't find a sidekick right away, because often sidekicks are made in giant vats rather than found on the street or in an insane asylum. A really good sidekick only has to be able to say "yes master" and carry out your orders. The rest of the time he or she or it can growl or hiss wordlessly. Also, don't forget that your sidekick can be a cat or monkey to whom you constantly whisper your plans maniacally.
6. Gather or make your minions. Like sidekicks, minions are often made not born. You can either build them out of scrap (the old robot army trick) or convert regular humans into brainwashed followers via drugs, brain implants, magical spells, or just plain terror. When crafting your minions, remember that they are your responsibility! If you make yourself a clone army, be sure you have somewhere safe to keep them and enough food to prevent them from dying before you take over the galactic rim. Masters these days often opt for solar-powered robot minions because they're easy to maintain and don't destroy the environment. It's the master's job to destroy the environment, not the minions'!
7. Set some goals. A master always has one purpose in life which he or she works on obsessively. Maybe you want to destroy the world, rule the solar system, control the spice, or simply unleash chaos because it's fun. No matter what your goals are, start small and work your way toward the bigger prize. If you want to destroy an interstellar conspiracy, start by destroying just one planet. If your goal is to spread anarchy to the world, start by blowing up a few hospitals. And if you want to remake the world in your image, filled with worshipers who understand your specialness, why not begin by taking over one city? Get a toehold before you start sprinting.
8. Know your nemesis. Whenever a master steps up to the plate, somebody (usually a pansy-ass leader) will try to stop the mastery. Keep your tentacles tuned to sounds of resistance. Is there an underground group of humans living in the sewers trying to undermine your regime? Is there somebody who is also from your race of superbeings or is possibly an old colleague who has pledged to stop you? What about an alien or mutant who hides among humans and thwarts your every move? Once you've located your nemesis, you must crush them instantly.
9. Consolidate your power. You've turned your nemesis into Dobby the Elf and sung disco to him. The entire city is in chaos. The meteor is heading for Earth, and your assassination plot is working according to plan. At last your shining cities will rise on the horizon! Everyone will shout your name! Genetically-engineered dinosaurs will rule the seas!
10. Dominate! Rule cruelly but serenely from a throne on a spaceship, a hidden island, or possibly the burned-out remains of City Hall. Send your minions out to march in the street, and explain to your sidekick once again how everything is within your grasp. Your minion will either purr happily or drool out the words, "Yesssss, master." Possibly, if you've designed the sidekick to have intellect, he or she will remind you nervously that there is still that pesky little nemesis you didn't manage to track down. SILENCE! WE WILL CRUSH OUR ENEMIES!
10.5. Go back to 1. Curses! Foiled again!