Step 1: Open the Picture in Photoshop which you want to convert into black and white.

Step 2: Go to the Image menu and select Channel mixer option as shown below.

Step 3: In the Channel Mixer Dialog box first click on Monochrome to make the picture black and white. This option just makes the picture black and white but now we need to enhance the picture.

Step 4: To enhance the picture now move the three sliders in any direction till you get a good effect.

Here, is the final image