Um, youtube? Natalia Taffarel has a video on this, but I don't remember if it was on her dvd or...
In your info palette, you set on of the infos to be hsb.
Open image that you like/has ara that you want to take the color from.
Then you take your color picker tool, set to 5x5, and look for an area of color that you like.
Look for the darks(zeroish 5 b), and set a new swatch in your swatches palette.
Now, repeat for miditones(50%b), and highlights(100%b).
Make a gradient map, set at color mode, mask it out.
Notice, that this can not be used all over, as you have some reflections (hand next to a red shirt will have some of the red reflected on it, and it'll look bad if you use the same gradient all over, in these cases you make a gradient for a specific area).
Retouching is easy, it's just about building your references, and being patient and taking it one step at the time.