The actual act of becoming an Evil Overlord is not as easy as it might appear. Ok, you’ve read the Evil Overlord List and sworn by it, you’ve recruited your army of loyal minions, hell you’ve even been hollowing out your own volcano base, and it’s due to be completed next Tuesday. By all rights you should already be the all-powerful leader of the world for the sheer amount of effort you’ve put in. But no, all you’ve got is an unstable mountain, a unionised workforce wanting pay and a council of advisors who are all telling you to get on with it.
So what do you need to do to secure your supremacy? If your base is near a village or small town (if it is near a large town you haven’t read how to build your base, which is a little stupid of you), you should take over that town, converting the inhabitants to your side, or at least making them as scared of you as possible, public executions will work for this, just pick a few people a week, but make sure the town's population is growing fast enough to support this. Now you have control of the town you can tax them and use the money gained for your expenses (worker pay, equipment for nuke etc).
Now you need a name, it is a good idea to do things in this order since should your initial attack fail they will not be able to tell anyone who you are. If you want to give yourself a title, for instance, Doctor or Professor, try to make it official, actually write a Ph.D thesis etc, otherwise abstain from academic titles and stick to high-ranking military titles. General or Supreme commander work well, just make sure that your minions cannot get promoted above you, that would be embarrassing. Otherwise an aristocratic title would be excellent, Count or Lord are the two most favoured, of course you could go with Overlord, which is of course a pretty good title. You shouldn’t, of course, use your real name, apart from the fact that “Overlord Dave” doesn’t sound all that threatening, it allows heroes to identify you and analyse your weaknesses from your FBI file. In fact it might be an idea to fake your own death to avoid identification.
Now you need to make sure you can be seen as the all-powerful leader. Make sure you minions are brainwashed enough into completely obeying you, and that you have a healthy rotation of advisors, you should, ideally, actually listen to their advice. Do not forget the power of the speech, make a rousing victory inspiring speech, followed by free beers (give two speeches to half of your minions to avoid the heroes taking advantage of a drunk army), rule by fear, but do not make anyone powerful dislike you, if they do, or if anyone gains a fair amount of prestige, have them executed. At this stage you should also choose your wardrobe, remember to make it comfortable, yet functional. A black suit with bullet-proof armour underneath, protected by a few spells and several guns concealed on you would be ideal. Remember any capes or long flowing cloaks can get caught in doors and on rocks, you don’t want to be defeated due to an uninformed choice of uniform.
OK, now you are secure in power you need to go about taking over the world. Build your superweapon, capture a nuke, rally your troops, and cast your spells and don’t forget the ultimate rule: “no matter how delicious it is, the irony of a situation will always allow the hero to escape. Shoot on sight.”