Disclaimer: This is not a rant about overseas tech support.
Villains! Where do they come from? How do you handle them? It's easy to fall into the trap of throwing together a nameless, faceless NPC party that walks up to your players' characters and starts beating faces; Lord knows, I've done that plenty of times. It's not that satisfying, is it? No, what your players need are personalities to vent their hatred on.
But what about when your finely crafted - nay! - exquisitely crafted villain goes down in the first round? That's not good either. I've certainly experienced that, too.
How do you create memorable, recurrent villains that seem like they are a part of the world? How do you do it in a way that makes it seems like the players and villains are connected beyond their simplest tropes; "Hi! You must be Player Character. I'm Recurrent Villain! Nice to meet you, now DIE! MWAHAHAHAHA! O! I am slain, forsooth!" Juggling villains is more art than crunch; there are rules you should follow to do it effectively.