The ability to sharpen your images is a powerful tool. Used well, it can give your images the extra snap that makes them jump off the page. Used badly, it gives images the unpleasant "crunchy" look we see in all too many Sunday newspaper color supplements. In overdoses, it can make images look artificial, or even blurry. With that in mind, we leave you with two final pieces of advice.
First, it's better to err on the side of caution. Despite what we've said about output sharpening, an image that's too soft will generally be less disturbing than one that's been oversharpened.
Second, always leave yourself an escape route. One of the great benefits of sharpening on layers is that you can always tweak the layer opacity to strengthen, reduce, or even eliminate the sharpening.
Sharpening is definitely one of those things that improves with experience, and a considerable part of that experience can be gained from revisiting your earlier efforts and figuring out what went wrong. If you save an unsharpened copy, or use layers to do your sharpening, you can always go back and refine your sharpening to get closer to the result you want.