Bracket If You're Not Sure About Exposure
In a tricky lighting situation, or a situation where you've just got to get the correct exposure for the shot, the pros make use of the camera's built-in exposure bracketing feature. This basically sets up your camera to shoot multiple versions (as many as five, if you like) of your current scene using different exposures (some lighter, some darker) with the idea that one of them will be just right. It starts by using the suggested exposure reading taken by your camera (which your camera believes is the correct exposure, by the way, but it can sometimes be fooled in tricky lighting situations), then it creates another image that is slightly underexposed, and another slightly overexposed (so you've bracketed both ends of the original exposure). This greatly increases your odds of getting the perfect exposure, and since digital film is freehey, why not, right? You turn on bracketing right on the camera itself. For Nikon digital cameras, there's a bracketing button to the left of the viewfinder (it says "BKT" on the button). On Canons (like the 20D or 30D), you have to turn on bracketing from the menu itself.