In this very interesting video, SLRLounge contributor Lauri Laukkanen is going to show us three different techniques to increase the sharpness of an image in Photoshop.
Personally I prefer the first one (and I guess is the same for Lauri), but I use slightly different settings, like I stay between 1 and 2 in the High Pass Filter, and then I used Overlay, but at the end the result is the same.

(via Lauri Laukkanen)