A story without structure is like a house without a framework.  It all falls apart.  Structure is what keeps your story from getting muddy and confusing your audience.  Regardless of what structure you use, you need some sort of skeleton to keep your story together.

I have read all kinds of books on plotting, structure, and story.  All have different methods for completing a story.  Some start with outlining while others start with character development, while others tell you to skip both.  Yet all have the same basic structure designs.

No matter how you write your story, it must have a beginning, a middle, and an end.  I should note that there are those that say that method is old and out dated; however, no matter what they wish to call their elements, all stories start somewhere, end somewhere, and along the way there is a middle of the tale.  Without them, you have nothing.

Your beginning does not have to start at "the beginning."  It could start in the middle of an event, say a bank robbery or an awards ceremony.  It could even start before the beginning, say at the birth of the protagonist, even though the story takes place at the end of his life.  No matter where your story starts, it has a beginning, and it tells us who, what, when, and where.  This is where we get to know the score.  It is the set up to the story.  In short, your have to start somewhere and  you have to make us care enough about this particular tale to keep up paying attention.  

Likewise, all stories must have an ending.  If your story simply ends with no conclusion, you will leave your audience dissatisfied.  Happy or sad, your audience needs to know it is indeed the end of the tale.  Consider this, if I said I got up and went to work, you can honestly say, "who cares!"  You would want to know, what happened at work, what problems did I encounter, and how did I solve those problems.  In your story, your ending is how your protagonist solved his problems or how he was overcome by his problems. An ending to a story is simply a conclusion, not  when you choose to stop telling your story.

That leaves us with the middle.  This is more than just the place between the beginning and the end.  This is the heart of the story, the meat and potatoes.  This is where many a story falls apart.  This is where we need a little planning.   I will say that, unlike the blueprints for a building, one can deviate from the outline, especially when you are inspired by an idea.   However, that would require you to have a plan in the first place, and  having a plan to deviate from will help your story from wandering away from you.  

Now it should be understood that that this is the most basic of story structure.  There are many other elements that go into a story.  There are those we all know, and there are those that we may not be aware of, but that is for another day.  For now, let us remember that the beginning is the set up, the end is the conclusion, and the middle is our story.

I read a book on screenwriting written by a gentleman who read screenplays submitted to the Raindance Film Festival.  The author stated in all the submissions he had read, he never found a bad premise, only poorly executed ones.  It is an interesting thought.  To me this means that any idea, no matter how far fetched it may be, has the possibility of becoming a great story.  

Consider the premise that a storyteller continued to tell stories to keep her husband from killing her the next day.  You would have 1001 Arabian Nights.  A very old story indeed.  From that we get Aladdin and the Magic Lamp, Ali Baba and the Forty Thieves, not to mention Sinbad the Sailor, each its own story with its own premise, and one executed well enough that it has endured for hundreds of years.  But what if we took the storyteller out of the Persian king's bedroom and placed it in the Soviet Union, in the Black Market, or on Mars?    While each would be a variation of the same premise, it would provide all sorts of unique story lines, each with its own potential for memorable stories.  

The premise, in and of itself, is merely a launching point for your story.  How you 
develop the premise makes all the difference.  Let us return to 1001 Arabian Nights.  If the storyteller had been an old hag instead of a beautiful young virgin, perhaps the king might not have been enchanted with her long enough to hear the first story.  Or what if she had been any enemy agent, or a man?  Each one of these ideas might have worked for today's audiences, but in Persia hundreds of years ago, those story lines would be unthinkable.  If we really wanted to get demented, one could make the beautiful young virgin a male enemy agent from Mars.

So it is down to execution.  That premise alone, while demented, is not enough for a good story, but it does lend itself to enchanting possibilities; however, it is up to the author to develop what would happen.  To a demented elf's way of thinking, take your premise and play a what if game.  Consider different variables.  Make it different, but also understand, premise isn't the story, it is the starting point.
I have often wondered how it is that some books are published.  Even more so I wonder how some moves/TV shows get made.  You read the book and somehow never manage to make it out of the first chapter, or you get up during the show and watch the commercials (say where is that remote anyway).  Certainly they are not the edge of your seat story that sucks you in until you forget what time it is or that you have only three hours before you have to up for work.

So what is the difference?  What makes one so boring you can't  pick it up and the other one so exciting you are sorry when it is over?  It is the story telling.  Good story telling can overcome genre preferences, author biases, and even typos.  For example, while I was working on a story on my iPad, I printed up a copy to share with my friends.  Thanks to the app and auto correct, there were typos and missing words all over the place; however, because my friends were into the story, the only person to notice these errors was me.  My friends were into the story.  They wanted to know how it would end.  They wanted to know about certain characters.  They did not care that in was a "hot mess."

Books, movies, TV shows, and the lot, succeed or fail based not on the special effects (though some may argue that), the stars involved, or even the author himself, but rather how well the story is told.  Sometimes, if the story is bad enough, it actually captures our attention on another level, perhaps the freak show level (or recent times, Sharknado comes to mind).  Yet, for us as human beings, we need the story to entertain us and for us as writers, we need to perfect the art of story telling, to keep the interest of those we wish to entertain.  So here's to perfecting our craft!
Why do I write?  At one time in my life, I wrote because I was bored.  A late night job, alone with nothing else to do, or perhaps just not feeling motivated to do anything particular.  Whatever the reason all it took was any piece of paper and a writing utensil to entertain myself.  Oddly enough, it would also entertain anyone who found a carelessly discarded napkin.  Needless to say, though it entertained me (and maybe a friend or two) it was never all that great.  Later, when I wrote my first screenplay on a dare, I found that I really enjoyed creating stories for other people.  Now, after over fifteen years of studying the art of story telling, I write because I want to tell the story I like.