Warm or Cool?
When I take photos, I always think about whether I want to create a warm image or a cool one (see Figure 2). For example, portraits often benefit from warm light, as it's flattering to the skin. Cool light has the opposite effect; it can make someone look cold or ill. If you use your camera's auto white balance setting, the camera will try to create a photo with a neutral color cast. To create a portrait with warm tones, select the cloudy or shade setting instead; either setting will make your portrait look warmer.
Figure 2 The same image, processed in Lightroom with two different white balance settings. I used 3023 K for the top image and 11624 K for the bottom. These settings are extreme, but they suit the abstract nature of the subject. There is no right or wrong white balance setting here; it's just a matter of preference.
You can use these two settings in other situations too, such as landscape photography. The best landscape photos are normally taken at the end (or the beginning) of the day when the sun is low in the sky and the light has a natural warm color cast. The warmth of the light is appealing, but if you use auto white balance the camera will compensate for the warm light and give you a neutral image. Use the daylight white balance setting instead, to capture the landscape as you saw it, or use the cloudy or shade setting to make it even warmer.
If you're taking photos of something like ice patterns in a lake in the middle of winter, you'll probably want an image that feels cool rather than warm. To achieve this look, set the white balance to daylight and photograph the ice under a cloudy skyit will have a natural blue cast. To make the image even bluer, try using the tungsten white balance setting and see if you like the result.