Watch the Light
Photography is all about painting with light. Yes, the camera will take pictures even in the glare of the midday sun, compensate with automated features like white balance, and produce a flat, washed out picture. Avoid shooting in such conditions. Wait for the sun to go behind a cloud. Or wait till the sun sinks lower, casting that much more appealing golden glow as the shadows lengthen.
Learn to look for subtle shifts in light, and study the effects on objects around. Your photography will improve vastly with attention to and understanding of light.
Understand Aperture and Depth of Field
Next to light, the most important aspect of a picture is the subject. To create a dramatic focal point, skilled photographers use aperture and depth of field to manipulate light, and control which part of the picture will be in sharp focus, and which will be blurred.
The aperture setting controls how much light will be let in, and this in turns controls depth of field. A smaller aperture number translates into more light and a shallower depth of field, so that only the subject is in sharp focus and almost everything in front of and behind that plane will be blurred ( for example, if you use an aperture of 5.6). A bigger aperture number translates into less light and greater depth of field, which means more of the field is in focus ( if you use an aperture of say, 22).
Understand Shutter Speed and Freezing of Motion
Shutter speed controls the length of time that the shutter will be open, and therefore also controls the amount of light let in. Shutter speed is defined in fractions of a second. The higher the denominator, the faster the shutter speed, and lower the amount of light that is allowed in. Faster shutter speeds also serve to freeze moving subjects, and are often used for this purpose.
Shutter speed works in combination with aperture to control the total amount of light let in. Therefore, there is an inverse relationship between the two. In bright light conditions, if you need to use a large aperture and shallow depth of field to blur all but the focal subject, then shutter speed will have to faster, to reduce the total amount of light.
Understanding and Using ISO to Advantage
ISO (or ASA) traditionally defines the speed of film. The lower the number, the slower the film, and slow film required more light to shoot acceptable pictures. The higher ISO numbers, like 400 and above, were used rarely, for low light conditions.
The unique advantage of digital photography is the auto ISO setting. While earlier film photographers used the trick of manipulating film speeds by a couple of stops in processing, the auto setting in digital cameras makes it extremely versatile in low light conditions. Automatic ISO settings go to up to 1600, resulting in pictures in situations where film cameras would have been put away because the light was too low to take pictures without using a flash.
The difference between two pictures of the same subject is the eye of the person who shoots the photograph. Using all of the tips mentioned above; aperture to control depth of field, shutter speed to freeze or allow motion, ISO to use low light to dramatic advantage, a good photographer will compose a picture in such a way that it showcases his or her unique view point of the image. There are a few rules to composition like the rule of thirds, but the most important is the unique eye that you, as an artist, see the image with.