Ignoring the histogram
It’s easy to get caught up with composition and focusing, and to forget to check the histogram regularly. But getting the exposure right in-camera is far better than trying to fix things later. Don’t rely on the image playback alone to judge the exposure, as the brightness of the LCD itself can give a false impression of the brightness of the shot, especially at night, or in bright sunlight. If a histogram is cut off or ‘clipped’ at either end, this indicates there are areas that are pure black or pure white, and so contain no texture or detail (in other words, areas that are under- or over-exposed).
If you find that the preview of the image displayed alongside the histogram is too small, then try the Highlights display instead. With this enabled, areas that are potentially over-exposed will blink on the display.