For a followup post read
http://ralphnordstromphotography.com/wordpress/articles/how-to-articles/expose-revisited/
The light meters in our digital cameras don’t always give us the best exposure. That’s not to say that they give us the wrong exposure. But the ‘correct’ exposure doesn’t necessarily produce the best image file as far as post processing is concerned, especially if we’re shooting RAW.
If you expose an image at the exposure selected by your light meter and check the histogram, chances are it’s skewed a little to the left, toward the shadows. This is especially apparent in low contrast scenes. The image might look great on the camera’s LCD and in Lightroom. But a slightly overexposed image will capture more information and is therefore better to work with later – given of course that it’s not so overexposed that you have highlight clipping. An ideal histogram is one that is just to the right of center. This technique is called ‘Expose to the Right,’ and is practiced by many of digital photographers.