Many times you are stuck with a washed-out photo from a digital camera or scanned photo. Most people who try, find that quick adjustments in Photoshop’s Levels or Curves dialogs will certainly boost the colors up, but they also destroy all the details in the photo.
Fortunately, Photoshop offers layer modes! Make a duplicate of the photo on another layer, the easiest way is hitting Command + J. Then, set the layer mode of the newly created layer to Overlay.
This should really boost the color & contrast, but not mess with your highlights and shadows. Of course, you can adjust the new Layer’s Opacity to control the intensity of the Overlay Layer.