Avoid tears
when chopping onions by not using a serrated knife as it causes a lot of eye-stinging sulphenic acids to spray everywhere. Use a flat blade kitchen knife and make sure it's sharp.

Oh, and get the fuck on with it. The less time you're handling it before it goes in the pan, the better as onion juice tends to make the ends of your fingernails take on a yellowish hue giving the impression that you spend a lot of time scratching your anus.
( sandettie light vessel automatic New Twitter - @bollocksreally, Tue 9 Mar 2010, 20:00, 2 replies, latest was 16 years ago)

Alternatively, wear contact lenses...
..and laugh at the puny onion's efforts to infiltrate your eyeholes :D
(Professor Kenny Martin Hmm? What?, Wed 17 Mar 2010, 17:33, Reply)

Also,
best to leave the onion for 10 minutes after chopping, before cooking, to allow maximum amount of thiopropanal sulfoxide (shown to be very effective against certain cancers) to be produced by enzymes released when onion is cut.
( Tab Hunter Make this useless process end and so, begin again, Thu 18 Mar 2010, 19:13, Reply)