While I’m sharpening an image, I have the most important part of the image in the Preview window—the owl’s eye, in this case.
Here are my two most important tips on sharpening: Don’t oversharpen, and sharpen last. If you oversharpen an image, your image will look pixelated. You want to sharpen last because adjusting contrast and curves also sharpens an image.
Another thought to keep in mind: Sharpen for viewing distance. As the viewing distance increases, you may want to increase the sharpness of an image; the converse is also true.