Avoid starting sentences with the same word as a nearby sentence, and paragraphs with the same letter as a nearby paragraph.

Don't make sentences too long. Just start a new one.

Learn how to transpose matter-of-fact statements/paragraphs into witty or memorable text by juxtaposing tones or images on what the reader was expecting. See Michael Lewis's books for an example, or Charles Stross's blog (antipope.org).