Here's how to go to grayscale by using Black & White:
1.Choose Image→Adjustments→Black & White. Your Black and White dialog box appears.
2.Adjust the conversion to your liking.
3.If desired, select the Tint button to apply a tone of color to the black-and-white image.

#photoshop 

Black & White Images in Photoshop
1.10 GEEK