The document provides guidelines for designing RESTful APIs including using HTTP verbs for CRUD operations, plural nouns for resource collections, associating resources through nested URLs, parameterizing requests through query strings and headers, supporting pagination, versioning APIs through URI paths and headers, and returning error responses with status codes and messages. Key guidelines include designing resources as nouns, using consistent and intuitive URIs, and making APIs self-descriptive through hypermedia as the engine of application state.