Another great book for new DMs is the excellent Dungeon Master for Dummies volume with tons of advice to run your first games or improve your skills as a veteran DM (always a good read, even for grognards).
The second piece of advice I have is to not try to run a "story" towards a precise "end". You are playing a game where players decide where their characters go next, and chances are they will choose another path to another end than the ones you thought about. That's actually what will happen in most cases.
You are not running a "story". You are running actual events, events with the players' characters as main protagonists. There's an important difference here, in that you are not working towards a precise end. The game isn't determinist in that way.
What can you do then, if you can't know how the game will end? You propose paths to the players, and they're the ones deciding where they go. When you prepare an adventure, you try to think about what the players' choices might be, and you do offer various choices (an adventure without choices is called "railroading", and it's very frustrating for players because they feel like they are just spectators and not actors of the events in the game). In any case, you know that most likely the choices of the players won't fit exactly one of the possible outcomes you imagined, but the ones you worked on help you improvise when the players make their choices in-game.
Grab a DMG and take your time. Read particularly the Chapters on Adventures, Running the Game, Campaigns and World-building. You'll find loads of other valuable advice there!
