This article is perhaps quite useful:
The 15 Minute Makeover: Photoshop Beauty Retouching
First part is quite easy. The second part is a little complicated.
Whatever, the key things are:
1. When retouching, always work on 100% enlargement of the image
2. Always use different layers. I found this out already and the major advantage is that it is non destructive to the original image!
