Wow, I'm really flattered by the responses!
Regarding a book, I don't think I have anything more to add to what's already been written (especially by Katrin Eismann).
About the technique I use... Almost everything I do is done one step at a time, on a seperate layer, with layer masks. I duplicate the layer and address one particular issue. Once I have that fixed, I duplicate that layer, and work on the next problem. So on, and so on. As more layers are added, I delete the older ones. I can tweak the changes I made by adding a layer mask. If I've lowered the layer opacity, I'll make a new layer, and merge the two to a single layer.
For example, when working on the face:
Add a levels or curves adjustment layer, and correct color and contrast. Clean up large blemishes with the healing brush. Lighten the area under her eyes with the clone brush set to lighten. Use the healing brush to go over that, to add back some texture. For smoothing the skin, I duplicate the layer and apply the Median filter (about 14), over that, I apply a Gaussian Blur (3), and finally, Noise (about 4). Then apply a layer mask, fill it with black (to hide what you just did). Use a soft brush with white paint, to paint on the mask. Revealing portions of the "fixed" image, just on the areas that you want to clean up. Flatten those two layers and tweak the opacity, so that some of the original shows through.
Of course there are more little tweaks and fixes, and they are all done using the same, duplicate, layer mask, process.
As you can see, I don't do anything out of the ordinary. The trick is to address each problem on it's own, and not go for a quick, global fix. You can do a global adjustment, but use layer masks to tone it down. The best advice I can give, is to learn how to use layer masks.
Hope that helps.
Vikki

http://www.lifetimephoto.com
http://www.pbase.com/vhansen/galleries