Lightroom Editing: Clarity Slider and Brush
I absolutely love this tool on Lightroom. It is such a versatile way to give photographs an extra bit of pop. The first image is just a control, to show what it looked like before any clarity, and is a RAW image converted to black and white.
The second image shows the effects of using the clarity slider in the basic menu. Now while this is an easy way to change the dynamics of the entire image, I wouldn't recommend using it on every image. If you have large blocks of a single muted colour, such as sky or a strong vignette, it will destroy the delicate colour gradients, and make the image look very over worked.
So I would suggest always using a clarity brush, which is shown in the third image. This way you have much more control over the implentation of clarity. You can avoid delicate areas that would otherwise be ruined, and instead focus on highlighting details which can create a great contrast against the more subtle elements of a photograph. Also of note, to make the results less harsh make sure you have brush density and flow settings at about 80% and feather at 50-70%.