The best piece of advice I've ever received was to shoot my photos overexposed and fix it in Lightroom, the second best was always remove your lens cap. By shooting overexposed your camera is able to capture a wider range in the lighter side of the colour spectrum, then in post you can simply reduce the exposure while keeping the detail.

On the left here you can see the photo above, but unedited, just to give you an idea of how some of my best photography starts out.