As with all other elements of the design, the key considerations for successful typography are clarity and readability. This applies to the readability of the individual fonts that you choose (a question that you’ve probably already dealt with while designing your logo), but also to the logical relationships between those fonts.
Typography is an important tool to help your reader understand the hierarchy of information within your design. Typically you will choose one display font (for short high-impact lines of text presented in large formats) and a body font (for longer text and paragraphs like the ones you’re reading now). You should generally not use more than two fonts, as this will prove confusing and visually distracting. (You may also choose to use just one font family and create hierarchy using font weight and size — as this website does.)
In the below example, the Medicare for All campaign uses a bold sans-serif font for slogans and headings (a very common choice for DSA campaigns) and a serif font for paragraphs which provides sufficient contrast to create a clear hierarchical relationship. (This example also demonstrates how color can be used to assist in organizing information, as in the red pull-quote on the top right.)
It’s important to choose two fonts which contrast but don’t clash. In other words, they must be sufficiently different to make their hierarchical relationship obvious to the reader but they must also look attractive in combination. Except in unusual circumstances, you will also generally want to choose fonts that have character but don’t draw too much attention to themselves — that means no novelty fonts!
Some fonts — such as Roboto, Lucida, and Liberation — belong to superfamilies, which include both serif and sans-serif versions. FontPair is a useful resource for finding attractive pairings of Google Fonts.
Size, Color, and Weight
The legibility of your text in a design is something that you should always check, especially when you place text in small sizes, using narrow weights, and/or using certain colors. White text on DSA red, to use a very common example, is less legible than black on white or white on black. For that reason, there is a greater limit on how small and how thin your text can be with a white-and-red combination.