We have already introduced some techniques to convert a picture into black and white, for instance in the section How to convert a photo into black and white (monochrome) 1. This time we are aiming to provide you more of a practical approach.
Select [Layer -> New Adjustment Layer -> Hue-Saturation] and press OK.
Now convert the picture into black and white (monochrome). Slide the saturation slider in the dialog box to the most right and set the numeral -100.
One thing to note is that you need to adjust the brightness to edit the contrast of the black and white image. There are various ways to make pictures black and white (monochrome), use them creatively depending on your preferences and picture types.