Direction, twist, wind are all important, but the key is the blow. Quick and sharp. Think the nasal equivalent of pulling a table cloth out from under a dinner setting: SNAP and the glasses stay standing, an indecisive tug and you've made quite a mess. Mechanically, it's kind of like an intentional sneeze without opening your mouth.

Your snot also has to have the correct...er...consistency. Don't try it for the first 15 minutes of your ride; wait until you've really got the juices flowing.

If you get really good at it, you can do both nostrils simultaneously, without even taking your hands off the bars.

Shave your beard before you start practicing.