Focused on a simple principle and designed to bolster writers' confidence and skills, writing coach at Harvard Business School Mark Rennella offers practical advice for students and budding writers -- with the goal of leveling the playing field between beginners and those with more experience. After a 30-year career as a writer, instructor, and editor, Mark Rennella has crafted a battle-tested method to help students and young professionals who want to improve their writing: the One-Idea Rule, anchored on the assertion that every component of a successful piece of writing should express only one idea. With The One-Idea Rule, writers embarking on their adult lives and professional journeys will have a reliable methodology they can easily remember and count on for all of their writing tasks, as well as increased confidence about the cogency of their writing and its potential for impact in the public sphere. Most advice about writing looks like a long laundry list of dos and don'ts. For those already accomplished as writers, these lists can be a helpful addition to an already-developed communication style. But for teens starting college and young professionals entering the workforce, it can be challenging to wield such complex advice to tackle increasingly demanding writing assignments. The One-Idea Rule is a writing primer aligned and empathetic with any young writer's needs.