Book writing companies typically select writers based on a combination of factors. These include the writer's expertise and experience in specific genres or subjects relevant to the company's projects, their writing style's compatibility with the client's vision, their ability to meet deadlines, and their overall professionalism. Often, companies require potential writers to submit writing samples or a portfolio showcasing their previous work, which helps assess their writing skills and suitability for the company's projects. This selection process ensures that the chosen writers can effectively bring clients' ideas to life and produce high-quality content.