Today, at one of episodes TFTTF I’ve heard one great idea – if you’re shooting RAW and using histograms to judge your work – set your picture style to Neutral (Canon users). Nikon should have something similar. This will give you more faithful picture and histogram. This is because source for histograms is JPEGs and this doesn’t matter you shooting RAW or not. “Standard” picture style will give you more contrasty picture with boosted colors and not so correct histogram and preview.
P.S. Don’t forget to set clock in your camera to winter time!