We see the world in color, and most photographs today reflect that realistic outlook - or something close to it, thanks to apps like Instagram and Hipstamatic. But there's something timeless and visually arresting about a well-crafted monochrome* image - even in the digital age when color has never been easier and more natural. Simply put, a good black & white photo stands out from the crowd.
So why would you choose to restrict your photos to shades of gray? When the subject is a rainbow or a bunch of colorful balloons, normally you wouldn't. If color doesn't add anything important to the image, however, there's an excellent chance your photo might look better in monochrome. If the subject of the photo has very little color in it, and if the color that is visible is simply a distraction, monochrome is a great choice. Another instance where you might choose to eliminate color is when the shape, texture or lighting of a scene are more important than its color. You can use black & white to make the subject seem timeless, removing obvious clues about the age of the photo, or even applying aging artifacts like virtual scratches or a sepia tone to heighten the effect.
Black & white can also serve to mask undesirable aspects of an image. If the subject is a person with a lot of wrinkles, or someone with a less-than-perfect or ruddy complexion, creating a monochrome image can smooth over minor cosmetic issues, especially if you also apply a skin-flattering yellow filter. Occasionally, when I run into a photo that has difficult lighting and no amount of tweaking corrects the color satisfactorily, I'll just go "artistic" and convert it to black & white. That might be cheating a little, but it's a useful last resort to save an otherwise good photo.
Now that we've looked at some reasons why to consider using black & white, let's consider the how of doing so. One obvious way to get a black & white photo is to shoot it using black & white film. There's simply no more direct, traditional way to produce a monochrome photo. When film use is impractical, you can either shoot the photograph digitally as black & white at the outset, or you can manipulate it in post-processing. Many higher-end cameras will let you select black & white at the time a picture is taken; some will even display the scene in monochrome in the viewfinder, which removes the distraction of color even as you're composing the picture. This can be a helpful approach, especially when you're not accustomed to thinking in terms of monochrome.
The precise technique you use depends on your preferences, as well as the hardware and software you have at your disposal. If you own a camera that shoots in RAW format, you have the most flexibility because all of the available data about each photo is in there, ready to be skillfully extracted with the right tools. Failing that option, all modern, consumer digital cameras can produce a JPG file, and this file can be converted easily after the photo is taken. So even if your camera doesn't "do" black & white as a native function, you're not stuck in color.
If you're using a dedicated camera, the easiest thing to do is to copy your photos from your memory card to your computer. You can then use software to "desaturate" your photos, with varying degrees of fanciness. A free program like GIMP will offer a few basic options to convert your photo, and that may be all you need (along with any desired exposure adjustments), to get the results you want. More advanced software, such as Photoshop and Lightroom, give you much finer control and a variety of presets to choose from. If you want even more creative control, check out Google's Silver Effex Pro, which is sold as a bundle with other useful plugins. This is the software many pro photographers use for achieving a classic look.
What if you're using a mobile device to shoot and edit your photos? You have a growing number of apps to choose from. Two of my favorite apps are Snapseed - available for free from both Google Play and the Apple iTunes Store - and VSCO Camera - a free app for Android and iPhones (additional effects filters can be purchased inexpensively). Both apps allow you to manipulate your photos in a myriad of different ways. Another Android-only app I enjoy is Vignette, which has an Ilford Classic Black & White filter effect that looks terrific.
The next time you take a photo, ask yourself if this image might look better as black & white. If you have the time and inclination, experiment with converting it. You may find the resulting image looks better than its color counterpart!
*I'm using the terms monochrome and black & white more or less interchangeably here, since a majority of monochrome images today are, in fact, black & white. Of course, monochrome technically would also encompass any technique that renders image in a single tone - sepia, selenium toning, cyanotype, redscale, etc.