Use a Curves Adjustment Layer to make sure the image has values ranging from 0 to 255 (maximum contrast). Then add a Threshold Adjustment Layer to see what the image will look like as a pure black and white image. The default setting of 128 for the Threshold should be fine for most images. The image is looking pretty good already, but it can be improve with the dodge and burn tools.

Select the Background to make it the target. To pull out more detail in the image, the burn tool will be used to add more black detail, and the Dodge tool will be used to add more white detail.

Tip: Set the pressure for the Dodge and Burn tools at about 20 percent, which will allow you to gradually build you to the look you want.

Tip: The Dodge and Burn tools both have the option of targeting a range of values. The tools can be set to have the most effect on highlights, midtones or shadows.

Tip: Experiment with different brush tips. For instance, a soft-edged brush tip works great when touching up a Grayscale image that will be printed as a halftone, but when trying to convert the Grayscale to line art, a hard-edged brush tip may work better.