Typography rules are guidelines that help create visually appealing and readable text. Key principles include choosing appropriate fonts, maintaining consistent spacing, and using a limited number of typefaces. It's important to ensure that the font size is legible and that there is enough contrast between the text and background for clarity. Another essential rule is the use of hierarchy, which helps guide the reader's eye through the content. This can be achieved by varying font sizes, weights, and styles, such as using bold for headings and italics for emphasis. Following these rules enhances communication and improves the overall design.