Sorry for the delay. Getting ready to leave town for a few days, and the girlies aren't very considerate.
One of the better ways is like this:
3. Ad-Layer > HSB and bring Sat all the way down
2. Ad-Layer > Curves and manually tweak contrast in each seperate channel
1. Colour photograph
It is an absolutely wonderful technique. Does wonders for converting fleshtones. If you are not in the mood for Ad-Layer Curves, feel free to try Ad-Layer Brightness/Contrast or something else. Personally, I prefer Curves.
Remember: you can paint on the Ad-Layer. Let's say you have some sky and a building. Well, pumping up the contrast on the clouds destroys the building; and pumping up the contrast on the building destroys the clouds. Just paint!
4. Ad-Layer > HSB with Sat all the way down
3. Ad-Layer > Curves with clouds manually tweaked and painted in
2. Ad-Layer > Curves with building manually tweaked and painted in (basically an inverse of #3)
1. Colour photograph of some sky and a building
Excellant technique to play with.
Gotta go!