There's so many different aspects to DMing I'll take the liberty of lumping a few together under some of the grades...grades that are, I might add, completely subjective and likely not at all what my players would give me.
A
World-building and Large-Scale Preparation. I intentionally try to get this bit right, because once a world is built - with cultures, history, climate, etc. - it's all just sitting there waiting to be mined for stories. And for each long campaign it only has to be done once!
B
Rules Knowledge. This would be an 'A', as the system I'm using is pretty much a homebrew that I helped design, but it's a 'B' because despite using much the same system for 25 years I still screw things up now and then.
Characterizations. I'm not bad at different voices and accents, though I tend to fall back on a few old reliables now and then; and coming up with rationales for why a given NPC is doing what it's doing is usually pretty easy. My in-party NPCs usually have clearly-defined character as well. But there's always room for improvement.
Plot and Story. Every now and then, inspiration strikes...
And it's made much easier by good world-building, see 'A' above.
Hitting the Curveball. Despite my engineering tendencies (see below), if the PCs go off the chart I can usually adapt pretty well. Same goes for if they come up with a new use for a spell, etc. or want to try something outside the usual rules. This ability comes from sheer practice.
C
Small-Scale Preparation. Half the time, I go into a given session just hoping it'll run itself, 'cause if it doesn't I'll be winging it. It's a bit better if I'm running a canned module - provided, of course, that I've bothered to read it first, and provided the module is complete enough to run without too much tweaking. The only time I do halfway well here is when I'm running an adventure I've designed and-or written, as I'm already familiar enough with it to react to what the characters do.
Railroading. I usually have a pre-designed vague storyboard for what adventure or story arc will come after what, and sometimes I let it determine what happens a bit too tightly. That said, there's been many a time when the players look at me and pretty much ask "what's next"...
D
NPC Combat Tactics. Far too often, the PCs win because I screw up the opposition tactics. This could almost warrant an 'F'.
Record-keeping. As I've become our league statistician, it may seem odd that I put this as a 'D'; but one look at my game notes will show just how woefully incomplete they often are. When I go to write up the game log a few days later, I'm usually going mostly from memory...and that's bad. Most of the time, I keep just enough notes to be able to assign ExP and know what date it is in the game world.
Distraction. I'm easily distracted. Just say 'beer'. Sometimes, for example, I distract myself (and everyone else) by telling war stories from old games in the middle of playing the current one...sigh.
F
Empathy With the Players. I usually have no idea which characters are important to their players and which are not. I just kill 'em all indiscriminately and only find out after the fact... And while I'm more than willing to celebrate great PC plays after the fact, during the actual game it's me vs. them...and I don't like losing.
Even after all that, I've probably missed a few key things. Interesting exercise.
Lan-"let the gods sort 'em out"-efan
