For a while now the conventional photography wisdom has been to expose to the right (ETTR) – to slightly overexpose to push the histogram to the right (highlight) side. ETTR is supposed to preserve detail in the shadows, which are on the left side of the histogram, while having little effect on details in the highlights.
This article is the clearest explanation I’ve seen of ETTR. The difference in the final image is very small, but it’s there. If you’re trying to wring every last bit of image quality out of your pictures it might be worthwhile. For everyday photography, not so sure.
This guy thinks that with a few exceptions ETTR is more trouble that it’s worth because it can cause subtle color shifts. In his experiments dropping the ISO speed by one stop improves the image just as much as using ETTR, without introducing color shifts or requiring post-processing.