More often than not books and workshop leaders (myself included!) tell you to always use a lens-hood to protect the front element of the lens and to prevent flare from entering and, thereby, softening and degrading image quality. As an aside, I've never understood UV filters as "protection" filters. Protection from what? Unless you're working near the coast with the threat of salt spray, why stick a cheap bit off glass infront of an expensive lens?!
There maybe times when backlighting is so extreme that you may even need to use your hand or, by using a remote release or self-timer, cast your body's shadow over the lens in order to cut-out this "problem" and retain the punchy-contrast of the scene before you. But why not, on occasion, let flare happen? By doing so, the image becomes softer, more pastel like and in some cases provides a truer representation of the image that first caught your eye.
