The document provides guidelines for writing different types of formal letters, including letters of advice, complaint, apology, invitation, and application. It notes the typical structure includes a greeting, use of formal language and the passive voice, and a closing with "Yours sincerely" or "Yours faithfully". Letters of advice, complaint, and apology follow a similar structure of introduction stating the reason, multiple body paragraphs with details, and a conclusion with closing remarks. Letters of invitation and application also have a standardized format with introduction, body, and conclusion sections focused on different relevant content for each letter type.