I hear the tendency to center compose. I stuck there myself for some time. If I were taking a shot of a frag for a wysiwyg website, showing the entire frag centered in the shot would be appropriate. But when trying to create a beautiful photograph, I look for visually balanced off center composition. And for macro photos, I find it is often the case that the photo is more effective when the entire subject is not shown. It removes some of the perspective which allows the user to focus on the textures, colors and composition without the preconceived bias about how something "is supposed to look".