White Balance
Usually, for raw photos, just leave your camera set to AWB - automatic white balance. For jpeg photos, use one of the settings on the camera. The video below describes how.
Lightroom 2
How to adjust white balance in Lightroom 2.
SET WHITE BALANCE
Select an image that you’re interested in working on, then press the D key to go to the Develop module. Press W to select the White Balance Selector tool. Hover the dropper over areas of the image that should be neutral (whites, grays, etc.) and look in the Navigator panel (top left) to see a preview. Next, click on an area that should be neutral, then drag the Temp and Tint sliders to make other subtle and subjective color changes to the image, if necessary. (from Layers)
