If you've ever watched a bartender put sugar (or salt) on the rim of a glass, you know that you need three things:
1) A glass. Obviously.
2) A liquid (often the glass is inverted and dipped in water or a citrus wedge is run around the edge)
3) Sugar or salt, which then sticks to the liquid
Step #2 warrants a closer look. I've found that the absolute best liquid for adhering sugar to a glass is honey. It works like glue! Just take a pastry brush dipped in honey (get rid of the excess), paint a line around the edge of the glass, and immediately dip in sugar. If you wait too long or put it on too thick, the honey will drip. Not cute when you're going for a nice, clean line.
Clean line of cinnamon sugar on a pumpkin cocktail. Yum!