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.
You will need your foreground color to be black and background color to be white making sure white is on top. Click on the paint bucket tool and click on the canvas (shortcut - press Ctrl + Backspace). The adjustment layer should now be black:
Now we want to switch the foreground and background to white on the top and black on the bottom. A quick way to get to this default setting is to press the letter D or click on the arrow between the two colors.
While you don't see the black on you photo it just hid the effects of the Level's adjustment layer.
Select the brush tool and make sure your foreground color is still set to white. Using a soft-edged brush, start painting with white on the girl's skin to bring some of that darker color back.
You may want to turn the opacity layer down to 50% for a less drastic look or maybe when painting the face:
Here is my finished photo: