This is going to sound really odd, but I actually use PSP8 to do all of the preperations on my icons, then I do all the texture adding, brush adding, text adding, etc in Photoshop CS. With that said, this tutorial is for PSP 8, but I am sure it's easily translated into PS.
I'm going to use this picture for the tutorial, so if you want to use it, too, then there you go.
The first thing I do, like always, is resize and crop my image. This is the image cropped, in case you don't want to go through those steps.
Then, I duplicate the layer and set it to screen 100%. Now, if your image is already really bright, you might want to mess around with the opacity of your layer. Then I merge visible.
Then, I duplicate the layer agian, and set it to multiply 100%. Once again, depending on what your images lightness already is, you may want to mess around with your layer opacity. I go to "Adjust > Blur > Gaussian Blur > 0.55", then I merge visible.
Then, I go to "Adjust > Brightness & Contrast > Automatic Contrast Enhancement > Lighter, Normal, Natural". After that, I go to "Adjust > Hue & Saturation > Automatic Saturation Enhancement > More Colorful, Strong". And voila, that's how I make my icons "crisp." If that is not what you meant, then it's just the images themselves, because I do nothing else to them. :)
This is what I did to it after I enhanced the quality / made it more "crisp." :)