Color to Black and White in PhotoShop

The gradient map tool maps a black and white gradient to the brightness values of your photo. Dark areas become black or dark grey and highlights white or light grey.
Photoshop CS and Photoshop Elements
 

1. Press ‘D’ to reset the foreground and background colours to black and white.
2. Layer > New Adjustment Layer > Gradient Map
3. Click ‘OK’

Pros: Quick and easy non-destructive black and white conversion
Cons: No control over the conversion