4. The Lair
If there's one thing that can be said about villainous bases, it's that it's all location, location, location. Ideally this should tie in with your chosen career. Wizards often have their towers, bosses of mega-corporations have their penthouses and their office blocks, tyrants have their castles. If you can afford something a bit more exotic, try an extinct volcano -- or an active one if fire doesn't bother you! Are you the master of ice? Then relocate to the frozen wasteland. It makes your job of killing the heroes that much easier when they're complaining about chilblains, frostbite and so forth.
Once you've got your base, give it a name -- a proper one. Look at Point Dread, Castle Plundarr, Mount Fear, Mount Doom... they're all evocative names. So what if it was originally 23 Railway Cuttings, East Cheam? That's no reason why it can't be The Dire Abode of Han-Cock, Donator of Blood! Name your lair after something that's fairly commonplace or distinctive about it, but again, try to be impressive. Round up any numbers to a nice big approximation. The Dungeon of a Thousand Blades sounds a lot better than The Dungeon of Sixty-Five Traps, Most of Which are Bladed.
Now, we can't all abide in abodes mentioned in the most ancient, darkest legends. It's your deeds that'll get them mentioned in hushed voices -- but what if you don't have the time? We all know how it is, minions need to be trained and equipped, traps have to be maintained and the dragons sure as Heck aren't going to muck themselves out! Why not just spread some rumours? The thing about legends is that, well, they're legendary. Everyone expects a bit of exaggeration -- the deeds of heroes are always sexed up a bit, so why not have that work in your favour? Okay, so you purchased a 25-room dungeonette with en-suite pit traps and deadfalls. Not in any legends yet? Just have the bards invent the myth of the Dreadlord Zovirax and his Dungeon of Unnecessarily Painful Death, into which he threw the most vicious and dangerous convicts whose spirits even now chill the blood of the living with their tormented howls. Adventurers love that stuff, and it's good advertising.