The four main principles of design are important when using typography.
Similar ideas should be close to one another to become one visual unit. Every visual element should link or align to another element on the page.
Repeat elements throughout the work. Repetition unifies.
In design, contrast is the most important technique available. Objects and text that differ greatly demand attention.
If you want to create a formal, quiet design, use typefaces that are similar in all aspects: weight, size, structure, form and style. This may appear boring and dull, however. Contrast adds interest. Using contrasting typography that combines opposite typefaces creates visually appealing, in-your-face design.
It's also important to organize typography in a design. Emphasize relevant facts according to the focal point of the message; organizing helps make sense of the central idea, directing the viewer to the important issues of your design.