A common myth is that one perfect exposure exists for every landscape, floral study, or wildlife portrait. But by under- and overexposing a scene, you can come away with two (or more) interpretations, each different yet compelling in its own way. Bracketing exposure—simple, thanks to auto bracketing on most DSLRs—nets you a decent exposure, several variations, and the potential to blend different exposures into a single, superior version of a scene. For really killer images, go a step further, if time permits: Bracket white balance, focusing, crop, and camera orientation (horizontal and vertical).
(From 5 Nature Shooting Skills April 2009 issue)