Adding a Tan
Find a photo of someone who could use a tan. I am using the photo below that I found online at http://www.reflexstock.com:
First we need to create an adjustment layer that we will use to apply the tan. On the layers palette click on the Create Adjustment Layer icon. Select Levels to create a new Levels adjustment layer.
In the Levels dialog box, take the gray input Levels slider and move it slightly to the right, toward the white one. Look at the picture while you slide. The picture should be getting darker. Stop at a point where you think her skin looks like it's got more color, but is still realistic. Press OK when you have your desired effect.
Here is my finished photo: