I could be wrong but I think the most important thing about being the DM (the 'art' as it were), is in the details. I think it's probably most important to make everything realistic (as far as possible), and logical.
Also, telling something very minor (like the dress of a passing nobleman), but
telling it well makes a big difference, IMO. I'm against DM railroading, because as a player I like to help *make* the campaign. Not the campaign world, just the campaign itself.
And as a DM, I find it pretty unrealistic to have all these huge plots just kind of fall into the laps of the PCs. Too unrealistic. PCs should be given bait. When they bite, you know it's time to real in. That's why I generally don't create complicated plots until I know what direction the PCs are headed in.
I won't bother to explain my current campaign plans, but suffice it to say that the PCs have a long way to travel across a vast expanse of settled (and unsettled) land, and whatever happens, happens. The details of the world are in place; they just need to bite on something, so that it's ultimately _them_ who control what happens to _them_.
