When developing a plot for your story, take the careful consideration to be inventive and unique. You want it to stand out to your reading audience or it will not likely succeed. The plot device chosen must be written in a way that later in the story the reader can recall what it was, but not to suspect it until it comes to complete fruition.
Where the plot device is placed can be alluded to further on in the story. Be careful not to throw out too many hints regarding your plot devise so as not to confuse the reader. If that requires that the story must be extended, than extend it. This is one of the reasons an outline is helpful. You can hopefully prevent bumps in the road while writing.
A good plot should be able to be written in one to two sentences. If it requires more than that, the plot is more than likely to complex, and you will lose your reader. A way to utilize a good plot is deciding it ahead of time. This will help so that all the details are mapped out and not lost in translation. Another technique that helps in the writing process move along is doing a lot of prewriting before you start putting the entire story together on paper.
Try to plan out each chapter with a brief overview of characters and milestones that will occur in that specific chapter. Furthermore, take the chance to develop a subplot, deciding which chapter to place it in, and how to resolve it.
An outline again will help to get the writing moving, and developing the plot and storyline progressing instead of stalling out. It may need to be revised but the plan is to just get started.
Ultimately, the plot is where, what happens, the extensive storyline, and that action that the writing ensues.