Regular granulated sugar's a fine stand-in for decorating sugar.
When shopping for gingerroot, look for a piece with smooth, unblemished skin and no signs of mold. Keep it tightly wrapped in the refrigerator up to 1 week, or freeze it up to 2 months.
Crystallized, or candied, ginger is gingerroot that's been cooked in sugar syrup and coated in coarse sugar. It feels dry to the touch but is sticky when chopped. In the supermarket, you might find it in the bulk-food bins, in plastic bags in the specialty produce section or in glass jars in the spice aisle.