Start by reviewing successful books in your genre and audience. A devotional, children’s picture book and practical business guide have different reading patterns and design needs. Consider how much text belongs on a page, whether illustrations are important and how portable the finished book should be.
Compare available printer sizes before finalizing the manuscript layout. A different trim size can change page count and production cost, so decide early enough for the designer to build the interior correctly. Your publishing team can help weigh reader comfort, format expectations and print specifications.