The scratchboard icon will be of the man only (the trees and junk surrounding the man will be deleted later), so drag a selection with the marquee tool that fits snugly around the man, and then choose Image/Crop.

Now the image needs to be converted from RGB to Grayscale. You could go to Image/Mode, and choose Grayscale, but you have no control over the conversion when using that method. A better way to convert to Grayscale is by making adjustments to the RGB image with the Channel Mixer, then converting to Grayscale.

After converting to Grayscale, the image needs to be sharpened with the Unsharp Mask filter. I used a setting of 500 for the amount, 4 for radius, and 2 for the threshold. Granted, the results from that setting are harsh, but this image is going to be used to make line art, and we needs to find those edges.

Tip: When using an image to make line art, ignore subtleties because they won't translate into the boldness of line art anyway. Instead, look for bold shapes and lines that visually communicate what the image represents.