The document provides guidance on choosing an appropriate writing style based on the purpose, audience, and subject matter. It discusses considering the purpose (such as informing or persuading), audience (whether you know them personally or not), and subject matter (whether it is factual or subjective). Based on these factors, it recommends choosing from several forms (such as reports, discussions, or instructions) and styles (formal, informal, personal, or impersonal). The goal is to use a style that clearly and explicitly conveys the intended message to the intended readers.