If you want to make a photo black and white, Photoshop’s Channels panel is your friend (look in the Window drop-down menu). You can mess around with the Channel Mixer, but if that doesn’t give you the effect you want you can do what I did here:
- Click on the Red channel (⌘3 on Mac). Select all (⌘A) and copy (⌘C).
- Click on RGB again (⌘2), deselect (⌘D), and paste (⌘V). Hide the new layer.
- Repeat for Green and Blue channels, then show all layers.
- Use layer masks and adjustment layers to blend the three layers the way you want.
In my example, I used the red layer on top for my shirt, the green layer in the middle for a smooth skin tone and darker lips, and the blue layer on the bottom (with a curves adjustment layer to darken it a little) for high-contrast eyes and hair.