There are many techniques for Portrait retouching but some of them are to be avoided if your goal is to get the most natural look possible .
Guy Gowan has some interesting techniques to get natural results:
http://www.guygowan.com/dvds/cosmetic/
I have this DVD and it's quite easy to follow. Each step is well explained and you don't need to be a Photoshop guru to understand these steps.
Excuse my naive question, as I've never used Photoshop (other than Lightroom), but does Guy Gowan teach his techniques to work on Photoshop or is it another application altogether?