It may seem old school or counter-intuitive in a color age to desaturate all the colors in post-processing but the qualities of the grayscale tonal range continue to be admired.
The Lightroom workflow to Black and White Conversion
Selecting the image to convert
Most of my street photography photos are immediately converted to black and white. I even visualize what they will appear like in black and white while composing for the shot. This being said, sometimes you find in a bad lighting condition another resort to convert to black and white thus salvaging your image. Furthermore, whenever I believe that the subject / story is more important than the colors, I chose to convert to black and white using Adobe Lightroom ("LR" thereafter).
Thinking in black and white will help you imagine the composition strength in your shot. Just press the "V" key in Lr back and forth to visualize every photo if it is a candidate to black and white or not.
Lr is equipped with powerful tools and sliders to achieve just that. Just drag the saturation slider all the way to the left and you have achieved a transformation of colors to black and white. It is that simple! But if you want to take your photos from good to great, there are many other considerations to include in your black and white workflow.
The Treatment B&W Panel
The B&W panel desaturates your images in one simple click. This can be achieved if you go under Treatment in the Basic Panel and select Black & White. The Auto button just underneath the sliders is a good starting point to your global adjustments.
There is also a Preset in your Lr Preferences that if ticket will automatically adjust all your B&W sliders mix based on how Lr sees fit. Just go to Preferences - Presets and select "Apply auto mix when first converting to black and white"
Black and White Presets
Lr offers 25 black and white develop presets. This is also a good starting point before you start dragging those sliders left and right. In the left side, under the Navigator pane you can find all develop presets Lr has to offer and the the first three sections are for black and white. These are powerful one-click conversion options to black and white.
The Basic Panel
All the sliders in the basic panel could be used the same way as if you are processing a colored photo. Which means you are adjusting tones, contrast, shadows, etc, the same way.
Black and white photos love contrast, so you can go crazy using this slider. Clarity also likes black and white and slightly moving it to the right might increase drama but beware to increase it too much for portraits as it emphasizes more the wrinkles and the pores in the faces.
The HSL/Color/B&W Panel
Even for black and white, these sliders comes in handy specially if you want to increase or decrease Luminosity in the people's skin color. Just click on the little dot on the left of the panel to "Adjust Black & White Mix by dragging in the photo". It works the same way in Tone Curve panel. Once activated, click on an area in the photo and start dragging up or down. If you drag left or right, the tool makes a slower adjustment to the sliders thus a more precise tweak.
If you have other input to the black & white post-processing just share it in the comment below. Enjoy the post... processing!