As we know there are a lot of different ways how to turn your colorful pictures into black and white. We also know there are several ways to edit gray tones in black and white. One way I sometimes use (in photoshop) is the following:
1. Open a color picture in PS.
2. Create Vibrance layer on top of the picture (background) layer
3. Create Hue/Saturation layer on top of Vibrance layer
4. Select (if not selected) the Hue/Saturation layer and slide the saturation slider to the left side to lose colors
5. Select Vibrance layer and start playing around with Vibrance and Saturation sliders to change brighter or darker gray tones even more darker or brighter (or change contrast in other words)
6. Once you found suitable tones, select all layers, Ctrl+E (in windows) to flatten image and save your nice colorless photo (always keep the originals, so make sure you do not overwrite the colorful file!!).