A quick crabby note - if you're going to spend at least $300 to see a historic performance event, like Wagner's Ring Cycle opening the new Four Seasons Centre for the Arts, could you not bring candies wrapped in cellophane, or bottled water still in the plastic bag from the grocery store? Or if you do could you at least try to be discreet about opening and consuming them and not crinkle and rattle loudly during, say, Sigmund's death scene? Also, turn off the alarm on your watch and don't check your cell phone or take pictures with your digital camera during the performance - can you believe that someone did that? Multiple times? They thankfully turned off the flash, but everybody behind them was lit up by the little display screen, and it was really distracting.
I tend to think that problem audiences are rude cocky kids who are used to watching TV at home, but there was a ten year old girl a few seats over from me who was better behaved and quiter through the entire Ring Cycle than many of the older 'proper ladies and gentlemen' in the audience.
Sneezing and coughing are natural and not really something you can help - although I really wish that guy two rows down didn't blow his nose at the key moment of resolving silence at the end of Gotterdammerung - but you can help making a racket with your cellophane-wrapped candies and velcro bags and zippers.
I know that the audience is what makes live performance special and that if I really wanted perfection I could stay at home and listen to it on headphones - but it's one thing to feel an audience around you as everyone is experiencing something great together, but it's another to have your concentration repeatedly broken by a bunch of philistines who can't shut up or sit still for more than ten minutes at a time.