I am trying to change the background color on several photos to just a plain white background. How do I do this?

well, the best way to do this i find is to erase all the areas you want using the fill tool on completely transparent pixels, using the magic wand tool to extract your part of the image you want to keep and then paste a white background then paste your image back over (on a new layer of course.) this is how i would do it, if i find a better way ill let you know. Oh and to variate how much the flood tool covers use the tolerance percentage in the flood tools side tab.