B&W Conversion with Channel Mixer

The "Channel Mixer" is also a great tool for Black & White conversions:

In case of multi-layered image, select the uppermost layer and "stamp" all visible layers by pressing [Alt+Ctrl+Shift+E] keys.
In the Effects panel, double-click the "Channel Mixer" thumbnail.
At the bottom of the dialog box that appears, check the "Monochrome" option. The image turns to grayscale.
Redistribute luminance with "Red", "Green", "Blue" sliders to achieve the best possible tone and detail (screenshot).
If you need a kind of "color spot" effect, add a mask using the "Add Layer Mask" command.