The story engine is the very heart of your story. If it is built well at the beginning it will power the rest of the development process and will drive the writing process.
Whenever there is a problem with a script or a story it usually is a problem with the engine.
Making sure you start with a good story engine is making sure you start with Gold.
The elements of the story engine in order:
Genres - The most basic type of story that you are writing. This will help you see the limitations of your story. More Info
Log lines - Short, Simple clear statements of what the story is about at it's core. Log Lines
Theme and Dilemma - What the story is really about and how the protagonist deals with it. More Info
Protagonist and Antagonist Conflict - The spine and main conflict of the story. More Info
Character Functions - How all the major characters function in the story relative to the protagonist and the overall story arc. More Info
See the Story Development Steps.