Here is my stock foto

India lady with dark skin ...

Okey ... we'll retouch her ... :P

1.

    -Duplicate layer

    -Blending mode = Soft Light 100%

2.

    -Go to Image >> Adjustment >> Selective Color ..

    -Add 20% black to Black ..

3.

    -Select skin areas using Magic Wand Tool ( Q )

    -Feather Selection ( Alt + Ctrl + D ) 5 px

    -Layer Via Copy ( Ctrl + J ) name it "skin"

Add an adjustment layer ( Curve ) ( Layer >> New Adjustment Layer >> Curves )

Level layer...

Duplicate some adjustment layer if it doesn't strong enough..

Hue/Saturation layer ...

4.

Colour her lip...

    -Pick Lasso Tool, draw the selection around her lip

    -Feather selection ( 5 px )

    -Use Hue/Saturation module ( Ctrl + U )

5.

And now, shade something ..

    -Stand on layer "skin"

    -Pick Burn Tool, darker some dark area ...

You see? these areas are so bright. Fix it now!!

     -Use EyeDropper, choose a skin tone color

     -Make new layer

     -Use Soft Brush draw into bright areas ( on new
layer )

     -Change Blending mode = " Color "

     -Filter >> Blur >> Gaussian Blur ( 5 > 10 px )

Yumm...

Now, we need some tone color for this image

I choose warm tone

Add one more adjustment layer ( Photo Filter ) and set as I did ..

At last step, you should make a copy-of-merged-layer by using Image >> Apply
Image ( on new blank layer )

Change mode = Screen, discount Opacity ..

You can use Dodge and Burn Tool to shading some skin areas are incorrect ...

This is stock foto

and this is last result !! Have fun :)