Here is what I do. Make a storyboard, or a basic plan of the story before you write it. Plan out the first few chapters before you write them so you feel more confident about them.
Everything everyone put down here is great advice. But mine is different. Put the story down, set it aside for a while. a half hour, and hour, a day, a week...however long is up to you. But when you go back to it (or before), decide how you want it to end and work backwards. :)