This candid photo was taken beyond the range of my flash, thus it is terribly under exposed.  In addition, there is a strong yellow cast from the overhead lights.  One of the morals of this example is that severely under exposed images can be enhanced significantly.
 

Fig. 1.  Before

Fig. 2.  After all of the changes below

First adjust the Histogram Levels
 

• Enhance > Adjust Brightness/Contrast > Levels ... (not the Brightness/Contrast).  While in this dialog box, you adjust the histogram range to enhance the image by sliding controls affecting the highlights, midtones and shadows. (See Figure 3a below and note that the histogram is all on the dark side.)
• Move the rightmost triangle under the histogram to the left to adjust the highlights.  In general, slide it to where the histogram is beginning to approach zero.  In this case, that is about 138 (notice the numbers that change).
• Move the left slider triangle a little to the right to adjust the dark areas.  In general, slide it just past where the histogram becomes positive.  Since this image is so dark, I did not slide it at all, thus it stayed at zero.
• Move the middle slider triangle to adjust the midtones.  I moved it to the left to about 1.44.
• Click OK.  (FYI: this will stretch out the histogram to cover the full range from dark to light, which is what Ansel Adams touted as the desired Zone System.)  The result is shown in Fig. 4 below.  Figure 3b shows the resulting histogram after this initial adjustment.
• If you do not like the results, click on the "Step Back (edit undo)" button.  In fact, you generally want to bounce back and forth with Step Back and Step Forward to compare the change with what you had before.  In addition, you should zoom in and compare the changes, particularly if the photo was taken in very low light.

Fig. 3a  Histogram of the original image

Fig. 3b  Histogram after initial adjustment

Fig. 4  Result after initial Histogram adjustment

Yellow Cast Removal:
Figure 4 is a big improvement over the original in Fig.1.  However, there is a pronounced yellow cast from the overhead lights.  In order to see the yellow cast more clearly, see Fig. 5 below, which is a close-up of the woman's face.  You can also see the yellow tint on the white tissue paper and the top of her hair.  Photoshop Elements has a menu item for removing a color cast, but it is very sensitive and often ineffective.  Figure 6 will be generated by removing the yellow saturation the following steps:

• Enhance > Adjust Color > Hue/Saturation.
• In this dialog box, first change the Edit selection in the upper left from "Master" to "Yellows."
• Move the center slider on Saturation to the left a fair amount to about Negative 40.  This will remove most of the yellow.
• Click OK.

Fig. 5  Close-up showing yellow cast.

Fig. 6. After lowering the yellow saturation

For the final touches, I whitened their teeth (see Edit Red-Eye + White Teeth page), and I used the Unsharp filter to sharpen the image a little (see Edit Example page).