The job of a writing coach is to help you develop your ideas into a manuscript. The coach does not write the manuscript. Instead, she guides you—in the way that makes most sense for your specific needs—as you write. The coach might work with you to develop an outline or a plot and then offer regular sessions to provide feedback on the material generated. Along the way, the coach will work to motivate you (by scheduling milestones, through discussion, and via review), and she will work to ensure that you are working toward your vision for the manuscript.
The coach may also help you with publication questions, guiding you in decision making about what publication route to take and in how to prepare for the book launch.
If you’re having trouble (a) getting started with your writing project, (b) making progress, or (c) finishing your project or if you find the writing process daunting or puzzling, then a writing coach may be exactly what you need.