I've created an icon in Illustrator for an iPhone app.
When the icon is in the size for the iPhone, parts of the graphic fuzzy. How can I improve the details on the icon? My icon is a clock, and it looks fine except for the hands.
Icon design typically involves managing pixels very tightly; it's a little more complex than just getting a good graphic, scaling it down, and exporting.
Go into View > Pixel Preview to get a better sense of what the graphic will look like when you move it from a vector format to a raster. This is assuming that you're not scaling the graphic in your Save for Web dialog.
You'll notice that sometimes straight lines can end up in between pixels, and so instead of one clear row of pixels, you get two fuzzy rows. That sort of thing might be your problem.
There are a few settings that deal with pixel problems. View > Snap to Point is one; "Align to Pixel Grid" on the Transform palette is another (though sometimes this can create more problems than it solves). Others may be able to provide more technical tricks.
If you're still stuck, look at clock icons that exist and work. Zoom in and see what they're doing with their limited pixels.
Are you scaling the image down after you've rasterized it? This will cause it to be resampled and not as crisp. Try importing your vector art into Photoshop at the exact size it is being outputted. (or resize in Illustrator before exporting) Also, if using PS, you can use the sharpen filter to make it pop a little more.