Quick View At Duotones

Overprint color: This will show you the range of color being overlay-ed on your image from highlight to shadows.

After Selecting what Type of tone range you want to work with, Double click on the ink 2, 3 , or 4 option and select your tones.

duotone 3 Quick View At Duotones

The tone selected can also be modified using the curve option box, by double clicking. Curves allows you to adjust the tonal range of an image to give you a greater range of adjustments. If you are not familiar with curves there are a few tutorials on the net that may help. In the mean time just play around to get an idea.

duotone 10 Quick View At Duotones

Also in the Photoshop Tutorials category