Here is a very important thing to remember, The GM is
not there to tell a story.
GMing is an art, and personally I feel it counts as an art in the same way as painting, singing, or movie making.
I highly recommend reading everything you can from The Alexandrian, particularly these three links,
http://www.thealexandrian.net/creations/creations.html
http://thealexandrian.net/gamemastery-101
http://thealexandrian.net/word...ames/dont-prep-plots
That last one is especially important for developing one of the most crucial of GM skills, the ability to run the game spontaneously without any prior expectation nor idea of where events are going to lead nor how they will play out.
Now it is possible to run a game along a railroad, and a good gm can do so without it
feeling too much like a railroad, but honestly, when starting out you should avoid that sort of game. The most important skill a gm needs, is to be able to spontaneously adapt to what the players are doing. The best way to build up and practice that skill is to simply not have anything in place that might encourage you to railroad the players, and that means running without a story plot.
You should consider the world as a character, the character you run, and thus your character "the world" interacts with the player's characters.
Basically, do not have any idea or concept of how events will play out. Do not plan on the players arriving at certain places, at certain times, in certain ways. Just don't do it.
Instead, build the world, then place a few figures in the world that have goals the players will want to stop, and make sure the players find out about it, then let the players handle it however they wish.