Template:Set Black White Point
Click once on the white eyedropper and then click on a portion of the image that requires setting to white. Bingo! It should magically jump to white. If it misbehaves at all then it might be because it is sampling on the single pixel value that lies underneath the eyedropper. This eyedropper (and in fact all of PS's eyedroppers) takes its settings from the Eyedropper tool that is found in the Tools. The default is a single point value, but you would be advised to change it to a 3 X 3 average or something more realistic.
You might not get the perfect white point set immediately. In which case, close the adjustments dialogue box and then open it up again. This technique does not work iteratively in one go. It has to be done incrementally.
Repeat the process for the blacks.