One more thought that came to mind as a general philosophy:
I think I got my reputation among my players as a RBDM partly because I've stolen some nasty ideas from Story Hours that I've read and so forth. But I also think that a major component is the way that I portray my bad guys. If I've got a Big Bad of any reasonable magnitude, he isn't just a pile of points there to be knocked down by the PC's and his stuff grabbed. He is a fully fleshed out NPC with detailed motivations, resources and capabilities.
If the villian is smart (and most of mine usually are) then I spend a good deal of time with his "character sheet" sitting in front of me. I look at his feats, skills, spells, wealth, magic items and so forth. Then I look at what he wants to accomplish. I think about his general attitude and personality and how he would use what he has to get what he wants. I make short range plans and long range plans for him and backup plans where a goal is really important to him. I think about what happens if the PC's thwart some of these plans and what happens if they don't.
The result of all this is that the major enemies that the PC's encounter don't just stand there swinging their swords or casting Magic Missile until they die and get cashed in for XP. They often take the PC's off guard with their tricks and traps. They might have hostages to bargain with or seek to find out about the PC's families and friends to apply pressure there. They will bribe people to make the PC's lives hard or hire assassins to go after them if they have risen to a high enough level of threat. They will seek out information about the PC's capabilities and try to find ways to counter them. They will find old adversaries of the PC's and try and recruit them the aid in the battle against the PC's. They will try to engineer situations where the PC's only get to choose between the lesser of two evils instead of a clear choice of what is good. That way, even if the PC's win, they lose something too.
Now all of that sounds like I'm trying to screw the PC's at every turn. But I'm not, the NPC is. The net result is that the PC's learn to fear and hate the NPC, but also respect him. And their satisfaction when they bring about his downfall is unparalleled because they know that I played the NPC to the best of his or her ability. They EARNED the victory against this villian.
I'll also note that because I tend to have my big bad villians willing to wage a sort of "total war" against the party and any others who would thwart their goals, I don't tend to make them super powerful. Because they are willing to use their resources and capabilities in efficient and creative ways, they can accomplish more with less. My big bad guys are very rarely more than one or two levels higher than the PC's. Sometimes they are individually very weak compared to the PC's and are simply well connected politically.
Just as a brief example, I had a situation where the PC's (6th level) were attempting to reclaim an old silver mine from a band of Kobolds. The Kobolds were led by a 7th level Sorceress and there were about half a dozen Rogue 3's plus another half dozen each of Rogue 1's and Sorcerer 1's. Mind you, the Kobolds almost never attacked with even half of this force in any single battle. But through use of clever tactics and making effective use of their small size and ability to see well in the dark, they fought the party to an absolute standstill. Eventually the PC's managed to strike a significant blow against them (after about three full sessions of non-stop fighting) and the Sorceress offered a bargain by which her people would go elsewhere in exchange for their lives. The PC's agreed with a huge sigh of relief.
And then called me a rat bastard.
