And here's my first, very simple thing I do to try to make myself a better GM: Read More Books.
A few years ago a friend of mine began giving to me for my birthday a stack of books to read. These are not books I would ever pick up for myself, because honestly I don't read a lot of books. Or rather I didn't, and what I read tended to be a very narrow corridor of tried-and-true, fairly predictable authors. Thankfully I didn't just let these books sit on the shelves, but have been reading them each year.
You may think that the best benefit of reading lots of books is being able to rip off the plot, but this is actually the least beneficial aspect of reading books, because book narratives and gaming narratives don't match up well. I had a friend who loved book-style plotlines and was forever frustrated when players didn't emulate the genre in the way he wanted. He should have just written his own books, and I told him so.
No, the thing that you can glean from books is little nuggets of treasure to file away for later. For example, I read Dance, Dance, Dance by Haruki Murukami a couple of years ago. It's not a story that would make its way into any gaming adventure, really. But in the opening chapter there is a description of a location called the Dolphin Hotel that is brilliant. And I promptly copied the description down and used the Dolphin Hotel showed up in a later game.
More to come! Comments welcome!