(1) Don't get stupid wasted & illegal all over the street. The cops are going to roll out the "paddy" wagons; don't let them fill them. this year, let's celebrate our (varyingly dubious) Irish heritage with some dignity. Confine your naturally modest drinking to private property and bars. REMEMBER, DRIVING DRUNK IS WORSE THAN EATING LIVE BABIES IN FRONTA YR GRAMMA & THE POPE. Try to avoid getting caught by cops pissing in alleys, which will be difficult due to lack of portapotties. To avoid possible heat, take shady activities (like blunt-smoking) a few blocks away from the main area of revelry.
(2) Don't resist arrest. many riots begin when someone resists arrest. if you fucked up, take one for the team and go quietly, so the rest of us can get on with it (it being reckless drinking of course).
(3) Don't trespass, steal or destroy property. a big part of the reason the parade was canceled was because local businesses and residents got sick of crazy drunken tourists (and fellow residents) trashing the place. If it's not your shit, don't touch it. and for the love of god don't wander into other people's backyards; they may be armed.
(4) Avoid sexual harassment. Straight boys: don't grab, taunt, or otherwise threaten women, as they will enlist the help of several nearby sisters, boyfriends, and/or muscular lesbian buddies in kicking your ass and the asses of anyone else who gets in the way, igniting a massive barroom brawl that will spread like the Chicago Fire until the National Guard is called in. Instead, channel your drunken horniness into clever, witty, bondesque banter; comment on the sparkling personality, aesthetic grace, and probable high intelligence of nearby females, who will thus find you irresistible and likely drag you off to the nearest vacant bathroom stall for make-outs.
(5) Watch your buddies. you won't be able to prevent idiots you don't know from doing fucked up shit, but you can at least drag your stupid drunk idiot friend back into the bar. Don't let your idiot friends OD during the pub crawl, as their bloated body may cause hazardous blockage of available fire exits, leading to utter chaos and trampling deaths.