from "Living Cuisine" by Renee Loux Underkoffler
I have heard many wild claims for how to keep the tears at bay while cutting onions. I have tried them all with varying degrees of success (like trying to cure hiccups). I do not mind the tears, as long as no other fluids get involved (sniff, sniff).
One suggetion that I have found to be quite effective is to slice onions under running water, although logistically it does not work out to chop onions under running water because they wash down the drain. Another suggestion, which some chefs swear by, is to bite a chopstick while cutting the onions. This unusual techinque is to encourage breathing through your mouth, so the volatile oils of the onion do not sneak up your nose and irritate the mucous membranes and make your eyes and nose run. Otherwise, I find good ventilation to be a simple and effective solution.