It depends on the haircut as to whether or not you should cut with or against the grain when cutting a black man's hair. If you are cutting his hair short then you cut against the grain. For long hair it is with the grain. If you are cutting an afro you can cut either way. For more see this article on 'How to Cut Black Men's Hair': http://coolmenshair.com/2011/09/how-to-cut-black-mens-hair.html.