When you take a photograph, you are literally recording patterns of light. The very word photographycomes from two Greek words that together mean “drawing with light.” I believe this is the most important element of great pictures, but also something that's always taken for granted.
The type and amount of light in an image, the color that the light casts, and where the light is most concentrated will all impact the feeling your photos convey. You can, of course, control all of these variables very precisely if you use only artificial light sources, in a controlled indoor environment. If you’re using natural light (aka the sun), though, there are a lot of variables—mainly time, weather, and location—all of which will affect the brightness, clarity, color, and tone of the light in your photos.
A good way to experiment with the varying qualities of natural light is to choose a subject and shoot it outdoors at different times of the day. Note the variations that occur at these different times—the shadows, the highlights, and the overall color of the image. The time of day affects the intensity of light and the colors in a photo. If you’re taking a photograph in the first or last hour of sunlight in the day (also known as “the magic hour”), the reds and yellows will be much stronger in you results, and the shadows not as dark, as at other times of day. The magic hour is called that because it makes everything look beautiful and magical.
Take a look at the photo above. It's a great example of the magic of a sunrise and what it can do to your images!
A lot of photographers—especially people who use digital cameras—love a cloudy day, because it softens the edges of everything. But maybe what you’re shooting would benefit from the hard edges that a sunny day will give you. Experiment in different weather conditions. Sunlight looks different in different parts of the globe, too. If you get a chance to travel, bring your camera along and observe whether the light in your photos looks different depending on what city you’re in.
I think one of the keys to discovering and taking great photos is taking hundreds and thousands of pictures with various angles, different times of day, various camera settings, etc...and enjoy discovering what works best for you.