When a photo is not very interesting as a color version it's a mental trigger for me to try a black and white conversion. A photo may have a lot going for it with composition, light and so on, but the color look is just meh. Take this scene from St. Michaels, Maryland.
The sky has a blue-gray cast to it with a little warmth along the horizon. The water is blue-green-gray. This color mix isn't doing anything for the photo, and it gives it a sickly look. That's too bad because with the strong foreground element and the dramatic clouds it seems this image should be a keeper. So just like you would adjust a composition to eliminate distracting elements, let's get rid of these colors that are a distraction.
For the black and white (B&W) conversion I used Macphun's Tonality Pro. When doing B&W conversions I tend to use presets more than with my color photos. Since I don't work as much in B&W, maybe I don't have as refined a vision of where I want to go with an image. So I poke around with presets until something clicks. For this photo I used the Sleepy Forest preset (as a lover of the outdoors, that name conjures wonderful woodsy scenes in my mind). The preset got me most of the way done, however the sky was still too light. I wanted a bit more drama to match the dark, heavy feel of the pier. While still in Tonality Pro I used a second layer with a gradient mask to darken the sky, and I had the image.
Processing: Lightroom, Tonality Pro (save 10% with discount code COREYHILZ)
Camera: Nikon D2x
Focal length: 52mm