|One of the key things is to click "view gamut" and see if anything turns gray. All the gray pixels are "out of bounds" and will print differently than they appear on the screen. We are used to supersaturated colors and a wide gamut when we work with digital images, but printer inks have not been able to keep up. When you get clumps of those "out of gamut" pixels, they will often print as artifact or look jaggy or clumpy. That's the printer trying its best to print, but often moving all the pixels to just within range (and they all wind up being the same and thus look clumpy).
You have to goof with saturation, hue shift, etc to remove these pixels. I found that if you select the "color range..." box, there is a selection in the drop down menu (somewhere) where you can pick "out of range" and it will select all those pixels. I wish I had known that earlier...
This, by the way, is for a picture that is meant to be on the wall. If you have lots of pix and are printing 4x6 or something, I'd just forget it. As long as you haven't upped the saturation but +20 or +30 (as we are apt to do), you probably won't have too much of an issue.