When in the writing process an editor is helpful
Although an editor is not necessarily needed throughout the whole process of writing a work of extended length, editorial help can be useful at any stage of the endeavor.
At the beginning. If a writer only has the loosest hold on a concept with just a couple of vaguely conceived characters in mind, an editor can be of help at the ground floor level, joining with the author in formulating plot structure, giving shape to characters, and generally kick-starting inspiration.
In the middle. If a writer is stuck somewhere along the line, an editor can work with her or him to help clear a viable story line path. This is most common in the second act of a script or treading into the middle of a novel after main elements have been established. Characterizations need to deepen and plot should build. Toward the middle of longer stories writing can become as swaybacked as a tired old dray horse.
After the first draft. When a first pass is completed and the author feels there's something lacking, but is unsure of what's needed, an editor can help find a "spine" in the story to give it stronger direction.
Before heading to market. The final red pen line editing, including word, phrase, and dialogue change suggestions, helps make a story shine its brightest.
