Adjustment Layers for Shadow Balancing

Debi wrote Photoshop 911 with this problem of under exposure in her photographs:

 > Hi, I have a picture of my wedding reception.   
 > Becuase of the lighting around the room, the  
 > Can you tell me how to lighten it, without changing us?  
 > background of all the pictures look dark.   
 > I am a little confused on the layers.   
 > Then a duplicate layer where I did some adjustments  
 > What I have so far is the main layer that I did not  
 > do any changes to.   
 > to our skin (named skin).   
 > Thanks so much
 > Please tell me where I go from here to follow your steps.   

Concept: While the following does not use wedding pictures, the basic premise is the same. Areas of the photo are overly dark due to under exposure. You'll need to mask the 'good' portion of the image, and raise the levels in the dark portions.