Avoid bright light and shadows
In essence, photography is all about painting with light. And getting just the right amount of light is critical to capturing a great photo. Most of the time, your digital camera does an admirable job on its own, but occasionally it needs some help. Factors such as the time of day, where the sun is positioned in the sky, and how much light and shadow appear in the viewfinder all contribute to the quality of your photos.
Consider this photo, for example. At first glance it looks fine. If you inspect it more closely, though, you'll see that the harsh midday sun has caused the subject's face, arms, and legs to be badly overexposed.
But that's okay, because you can fix such problems (or avoid them in the first place). I have an assortment of tips to help you make the most of your lighting when you take the photo, as well as to help you correct bad lighting situations with your image editing program after you get home.