Skin enhancement is a technique often required for both photograph improvement and photo manipulation.
Here is a Photoshop action that gives a fairly dramatic improvement to the skin, but the layers are not merged during the action, so you can make alterations to the adjustment layers used to your liking. Also consider reducing the opacity of the final image over the top of the original so the effect is not so drastic. It is an action to be experimented with according to which photograph you are working on and the final result required.
Click on the image to download the action.