Know the Purpose and Scope of Your Document
Before you begin writing, know the purpose for which you are writing and what you want your document to accomplish. As you write, keep your primary objective in mind (you could even type it at the top of your document and refer to it throughout the writing process, if needed; you can delete it when you are finished with the initial draft), and never stray from it. However, if in the course of your writing you discover that your focus has changed, that’s okay. Simply make sure to revise your writing as needed to reflect your new purpose in order to maintain a clear, coherent document.
Tell readers early on how they will benefit from reading your document—what they will be able to accomplish, what information they will be able to gain, what product or service they will be able to purchase that will make their lives better or easier, or in what other way they will be able to benefit from reading your document..