Your image is soft--the 100% is showing you. There are two things that are really going to help, contrast and sharpening. You should always change contrast before sharpening.
Here you want to use curves. Curves is simple. The box shows black at the left bottom and white at the top right. The diagonal line is the image. If the line is moved above the original position, the image gets lighter. If the angle of the line is greater than 45 degrees, the contrast increase.
I looked at your image. Open it up.
Go to a point at 2/3 to 3/4 to the top of the line and move it slightly up--you should see the highlights and mid-tones lighten. You should see an increase in contrast as well. The reason I started to the top is that most of the tones in the image are toward the bottom--the histogram seems to indicate slight underexposure. By moving the top of the curve up, I am moving the lighter tones to where they should be and the mid-tone and shadows should follow nicely.
Now, if the shadows and dark areas seem a little too bright, and they did for me, click on the lower section of the line and bring it down to meet the original line position--you should see a deepening of the dark tones. I found going below the original line position made the contrast too harsh and your blacks blocked up--this is not surprising as the image seems underexposed. With this image, you may not want to hard a black--the black T-Shirt blocks up fast making it look like a black hole. You can keep moving these two points to refine the curve.
When you get the contrast right, it is time for unsharp masking.
This should be done at 100%
I found that a percentage of about 40% worked well for your image at a radius of 1.0--if what you did with the curves is different from what I did, you may need to go higher or lower with the amount.
With unsharp masking, the effect is subtle. When you click the preview button on and off, it should look like someone is wiping of a thin layer of grease from your image. Thing just tighten up slightly.
Now one thing we have not covered is what is happening to the image through the printer. If what you are doing here not the problem, we can talk about how this image you posted is different from the printed image. That might be a color management (CM) issue. Usually that is manifested as an unexpectedly large shift in contrast and color saturation usually cause by a profile mismatch.
Originally Posted by gardengirl13
OK here is an example of one that I think printed quite badly. Looking at it at 100% is scary!
Now with the 60D set to higher levels of USM it would have printed fine up to 16x20 (again sorry I don't have the camera any more so I can't really compare. But I have many photos set to the normal levels I'd use and those prints are great.) I can't remember what settings I had the camera set to, probably normal to low sharpening.
I've never been good with photoshop so I'm not sure what to do to make it better, which is why I'm asking here.