Most people when they want to sharpen their images with photoshop they use the USM (Unsharp Mask filter), however there is another powerful photoshop filter that in my opinion does a better job.
I am going to start with a closeup of a flower that I took handheld
Here is a 100%crop of the picture before using this technique
1) Open the photo you want to sharpen and make sure you are viewing it at 100%
2) Duplicate the background layer by hitting Ctrl+J or just go to Layer-> Duplicate Layer
3) Now it’s time to apply the High Pass filter at the duplicate layer. Go to Filter-> Other -> High Pass. I usually use a radius somewhere between 9 and 12. In this case I used a radius of 11.5
Now your image should look like this.
Change the duplicate layer mode to either overlay,soft light or hard light. Play with the blending modes and the opacity (I usually use values from 30 to 70% ) of the duplicate layer until you are happy with the result
In this case I used Soft light and an opacity of 60%
Here is a side by side comparison of the original versus the modified