Meter correctly for the situation. I don't mean that in a snippy sort of way; as I said, your camera's meter assumes that it's looking at middle grey, so when the subject is in reality, bright white, it will invariably come out looking like a muddy, grey scene. The best way, IMO, is to set your camera to 'Manual' and metering to 'Spot'. Now, meter the palm of your hand and then add one full stop (This is because average caucasian skin is approximately one stop brighter than middle grey), that is, if the camera indicates that you need an exposure of 1/125 @f8 for a correct exposure, then increase to 1/250 @ f8 or 1/125 @ f11, or an equivalent combination.
This will get you in the ball-park, and you can tweak your exposure slightly as necessary from there.