I have not posted the Photoshop Technique for awhile so this post I would like to show you how to use LAB color mode to add realistic color saturation. Please follow my steps below. You can click each photo to see a larger photo.
See the "Before and After". You will see an awesome result of this effect.

1) See my photograph and you will see that the saturation is not that good. Firstly , I normally duplicate a background layer by dragging the background layer over a create new layer icon as below because you can go back to see the original photo or if you do something wrong with it you still have the original image.

2) Change the color mode to LAB (Image>Mode>Lab Color)

3) Then the program will ask you to flatten all layers into one layer. You must answer "Don't Flatten".

4) Then you can see in the channel pallet that there are 4 layers (Lab, Lightness, a and b).

5) Select "Lightness" channel and select the curve command (Image>Adjustment>Curves) to add contrast into the photo.

6) Adjust the curve to S-Curve shape to add saturation.

7) Select "a" channel and drag the bottom point to the right. So you will see that green tone is added into the photo.

8) If you drag the top point to the left, you will see that magenta tone is added into the photo.

9) Drag equally between the top and the bottom point to balance color tone added into the photo as shown below. You can see that the color saturation looks better now.

10) Select "b" channel and drag the bottom point to the right. So you will see that blue tone is added into the photo.

11) If you drag the top point to the left, you will see that yellow tone is added into the photo.

12) Drag equally between the top and the bottom point to balance color tone added into the photo as shown below. You can see that the color saturation looks
PERFECT now.

13) You may add sharpness into this photo (Filter>Sharpen>Unsharp Mask)

14) Adjust some parameters until you feel happy about a result. In this case, I use Amount = 50%, Radius = 1 pixel and Threshold = 0.

With Lab color mode, you can add the realistic saturation into you photos. It's nice and easy method. Any suggestions or recommendations are very welcome.
Cheers,
DSM