Any text-based layout is going to have one typeface used for the main body of type - this is called the body copy. Body copy is usually selected for its ease of readability, but line after line of the same type style, no matter how readable, not only looks boring but also tires the reader's eyes. Varying the type styles is a good way to combat this. You can break up your document into sections divided by headers. According the Poynter Institute's 2007 eye-track study, online readers look first for navigation aids when reading something on the web, so headers will help draw them into the text by giving them an at-a-glance idea of its contents. These headers should, in a few words, describe the content that follows it and be presented in a type style that contrasts the body copy.
Images are one of the top entry points for readers, according to Poynter and their thoughtful use can help your layout appeal to more people. For fixed-width layouts, the designer has two options: using an image at the full column width separate the type above and below it or insetting an image into the the column with the type wrapping around it. The former method is preferable when there's a transition in the type of content from the text above to the text below; separating the type like this will interrupt the flow of the text and hit a kind of "reset button" for the reader. The latter method is better for flowing narratives as the type wrapping around the photos will better integrate them in the readers' minds.
Salient quotes or passages are a good way to draw readers into a layout. They can be displayed either as insets or full-width type treatments in a type style that contrasts the body type. Readers might have enough interest in the quote to be pulled into reading the whole of the text.
Simple provide a little breathing room in a fixed-width layout, without having to worry about things like narrative flow and headers. You insert horizontal lines or bullet points whenever there's a good place in the text for the reader to take a break. It's not as elegant as some other methods, but sometimes a design just needs to be functional.