There are lots of ways to sharpen an image in Photoshop, and there’s really no right or wrong way. But there are better ways than others. I think you’ll find the following method to be interesting, and provide pretty good results. First, place a copy of the image on a second layer by hitting Command + J. Set the newly duplicated layer’s blending mode to Overlay. Now go to the menubar and select Filter>Other>High Pass. Use a starting value around 4 to 6. You can adjust the values to your liking.