Photography is about feelings and getting the viewer to focus on the important parts of the photo. The light and colors guide you but sometimes there is just too much. That could be the time to go monotone. Or if you don't have that much available light or you have the 'boring' cloudcast over you. As color photography usually looks best when you have a lot light available - put in black and white that light might be just what you need for the perfect mood.
Going black and white also teaches you to be a better photographer. Instead of using colors to lead you eye around the photo, you need to find a way to use the shapes and textures instead. This will actually help a lot with your color photography as well so it's a win/win situation.
Five tips for black and white photography:
- Shoot in color!
- Look for contrasts
- Look for patterns, textures and shapes. Remember, you don't have colors as your guide. ;)
- Use as low ISO as possible. This is what you usually do anyway but for black and white this is even more important. You get a lot more grounds to play with the tones in conversion phase. And if you want, you can always add noise. It's much harder to remove it.
- In post-processing, don't use 'desaturate' to make the photo black and white. Use channel mixer or Photoshop's dedicated black and white tool. That way you have more control over the tones. This is also why you need to shoot in color.
Sometimes the colors look very bland and the textures non-existent...
...but converted in black and white the image comes alive.
And last but not least some GREAT black and white photographers.
Now... Go shoot black and white!