It is said by so many distinguished photographers, most probably THE most important ingredient in a successful photograph is light. Without light there can be no photograph. It is therefore inevitable that light will always play a central role in any photograph. For me personally, light is rarely the focus of the photo, but it certainly is the major factor in determining whether a photo is awesome or just good.
Here is an example. I must confess, it is not the best photograph under the sun. Partly because I have not been in the right state of mind for taking good photographs the past 5 months, and party because I was a bit too late for the fall colours this year. Nevertheless, the photo below is not horrible either, and was taken at Stanley Park in Vancouver.
The first photo illustrates the composition, subject matter, and focal points. As I said, not the best photo in the world. While this image contains most aspects of what I wanted to capture at the time, it lacks one significant aspect - light. The lighting is very flat. It was cloudy and when the sun was hidden, everything was very dull.
I realised this photo was lacking punch, and was just plain boring. Sure one can see the fall colours on the trees nicely, but it was a photo one would just scan over and move to the next photo. Not what any photographer wants. Since I have been walking around the harbour for half an hour before, I knew that the lighting was changing rapidly. So I had my camera tripod mounted and... waited. Just waited. 3 minutes after I took this photo, the sun started breaking through the clouds. Look:
Right at the back of the sidewalk the sun caught the yellow leaved trees and transformed them into a magical showpiece of spectacular fall colour. Another minute later and I took this:
The light was getting stronger, casting awesome shadows due to the high latitude in Canada. The sun's rays caught the orange leaves and ignited an imaginary fire in the few leaves still struggling for survival. 20 seconds later and I had my final photo:
As I said, not the most awesome photo but compare this one to the first, and you will see the lighting transformed a dull photo to something magical.
Less on learnt: Be patient while you are out on a photography journey. Wait for the right moment.