The answer to the question "Once you acquire there two basic skills, you'll be able to transform a vague idea in your mind into a coherent piece of writing" is C - doing research and organizing your ideas.
Research and organizational skills are important skills to learn when writing a coherent piece. Most pieces of writing start as a vague idea. By researching your vague idea, you are able to validate it and flesh it out to craft a coherent piece of writing
