Photoshop Elements Tip: Sharpening images
Tips & Tutorials, by Mark White
November 23, 2012
Apply sharpening after all edits have been made using this long shortcut: Cmd/Ctrl+Shift+Opt/Alt+E
This creates a comped version of your image as a new layer. Then go to the Enhance menu and down to Unsharp Mask to adapt the sharpness of your image to crisp it up.
A layer mask can also be added to this layer for selective sharpening with the Brush and Eraser tools.