In human communication, content cannot be separated from form. Most students receive at least some training on how to shape the content of their message. In contrast, training on how to shape a message's form appears to be virtually non-existent. This is a shame: poor form weakens communication, and the human experience is diminished when the documents that we live with are ugly. Improve your life as well as the life of your readers by learning the basics of typography and graphic design! And remember: “Good artists copy, great artists steal.”
Shaping the content also matters, of course. The following resources are warmly recommended.