Obviously there are numerous ways to achieve any effect, and this is only one. I've taken all the following screenshots in Photoshop Elements 9, but the method is identical for all versions of Photoshop and Photoshop Elements.
I'll start with a standard "clean" photo, to which I've done a basic enhancement using a couple of Levels layers:
To commence the fun, I add a Hue/Saturation adjustment layer:
This makes the photo darker and richer:
In the Hue/Saturation dialog, the Hue slider isn't important for this method. I want to concentrate on the Saturation and Lightness sliders. Essentially, the Saturation slider controls the richness, and the Lightness slider controls the darkness.
The result is a lovely rich background, but not too overpowering on the subject. (I forgot to take a screenshot of the final result - d'oh!! Sorry.)
Let's take a look at another one.
First, with a bit of clean processing; then with the effect applied; then masked back a bit:
One more thing to mention. If you think the Multiply mode is fun, you should also try the next two - "Color Burn" and "Linear Burn". They give even stronger results. A bit too strong for my taste, actually, but you might love them!
Here's Rowan with the Hue/Sat layer on "Color Burn" mode:
And on "Linear Burn" mode: