I've used this exercise - find an image that really appeals, and try to deconstruct it - light, composition, angle, positioning, etc. Then try to do the same. Compare your version to the one you used as the inspiration - how close did you get? Were there significant differences? Where are the highlights and shadows? If your attempt is completely off, compare and try to see what you missed and what is the difference in feel - then try again.
Keith notes something that many good photographers do - keep an eye out for good locations and visit them often to see how the light works. I've seen a nice city skyline take on a very different look when photographed just before dawn, with the rose/reddish light from the approaching dawn illuminating the buildings with the fading night behind them - an image I've seen (and shot) many times, but rendered completely otherwordly by someone who noticed the same and got there in the right light.