To achieve that perfect skin look, start with a flawless model. If you can't afford one (or one doesn;t exist in your market), hire a good makeup artist. Sure, you can repair a lot of damaged skin in Photoshop, but why not start with a model that's close to perfect?
So, let say you're like most of us -- you don't have a perfect model and can't afford a makeup artist. What now? Follow the advice posted in this thread. The "before and after" image below shows Tiffany, one of my favorite models (forgive me Tiff). I used all the techniques listed in this thread
-- pumped up the contrast and saturation
-- used Gaussian blur and Diffuse Glow on her skin
-- used the Dodge Tool to brighten the jewelry
-- used the Image/Adjustments/Hue-Saturation to whiten the eyes & teeth
(I decreased the saturation of the red and yellow channel before increasing the brightness of the overall white)
-- used the Color Balance to make her iris more blue
-- used the Cloned brush to add more hair to cover her right arm
-- use thed Clone brush and Healing brush on her cheeks to smooth out the skin
All that said ... it helps to have some artistic talents.