Unsharp Mask - Good Settings To Start With

Scott Kelby recommends starting with the following unsharp mask settings:

People: Amount 150%, Radius 1, Threshold 10
Cityscape, urban or travel: Amount 65%, Radius 3, Threshold 2
General day to day: Amount 85%, Radius 1, Threshold 4

If you have Photoshop you can do the following to get a better result than just using unsharp alone.

Change the image to Lab colour mode. Select the Lightening channel and apply an unsharp mask with the settings above. Now apply the unsharp mask again and under Edit, adjust the opacity of thebsecond unsharp mask as required.