The story moves along. There’s a beginning, a middle, and an end. The protagonist meets colorful “helpers” along his way. The female lead is spunky and presents a major reversal. Sounds good, right?
But the middle has no slow build, only a series of episodes. How to fix this? Get out those 3×5” cards, the spreadsheet, a proprietary program—whatever it is you use. List all the conflicts your protagonist meets. Put them in ascending order. One very bad one for the middle where all seems lost and one super dramatic one for the climax. Don’t forget the small subplot and minor character story developments that can seemingly set your protagonist off in the wrong direction.
Once you have categorized and re-ordered your scenes in a development toward crescendo, rewrite the middle to reflect ongoing and increasingly challenging problems for the protagonist. Conflict builds tension. Tension keeps the reader…well…reading.
The French crime writer Fred Vargas does this very well. http://www.amazon.com/Fred-Vargas/e/B001I9OXT6 In the midst of a very large problem, some small conflict with a minor character prevents the protagonist from doing the next thing in a timely manner or overlooking a very important piece of information.
You will see a difference in the ability of your story to hold the reader all the way through. Then you are ready to write the ending.