Grabbed from cameronmoll

Usual unsharp mask settings are 120%, radius 1.6, levels 12.

I almost always convert the image to LAB color and unsharp the luminosity channel. This sharpens only the grayscale component of the image, not the color. This helps prevent unwanted halos from oversharpening. Then convert CMYK or RGB.

Unsharp mask from cameronmoll

Please, sweat the small stuff ~ Authentic Boredom
The Unsharpen Mask is great. However, try this method. After you have resized, levels and etc., duplicate your layer. In the top most layer, change its mode to Overlay. Now go to Filters > Other > Highpass. The sharpening effects as result of a highpass (in overlay mode) is much crisper (and more flexable) than the unsharpen mask. These is the procedures that third-party filters often use behind the scenes.