Now, first we will duplicate the layer. Once you've done so, select your quick selection tool.
Select all of Gwen's body, but leave out her hair and clothes. Make sure you use both the subtraction and addition options to get the best selection.
Your selection should look something like this:
Now we want to soften up the edges to create a nice transition for our effect. Go to Select > Refine Edge. You can play around with your settings, but overall you want a nice smooth, feathered look. Here are my settings if you'd like to match them:
Previewed, the image in the refine edges option should look like this:
Press okay and your image should go back to normal, still intact with the marquee. Now we're going to create this area into a mask, so select your Add Layer Mask button on the bottom of your layer palette. In doing this your marquee should go away and you should notice a new mask next to your layer. Creating a layer mask isolates the selection, so even though we add effects underneath it, that area we just masked will always stay the same and is never affected.
Now we'll begin adding the effects! Make sure your new masked layer is always on top of all the layers for the effects to work correctly.
Duplicate your base layer and set it to Vivid Light at 50% opacity.
Now go to Layers > New Adjustment Layer > Levels and match your settings to mine:
Your final product should look like this:
For other effects, try colorizing some layers or even adding textures or filters.