These are all good rules to keep in mind to prevent you from looking like a jackass at the bar/party or being a crappy friend. Some of my favorites:
29. If you owe someone twenty dollars or less, you may pay them back in beer.
31. If you have been roommates with someone more than six months, you may drink all their beer, even if it's hidden, as long as you leave them one.
34. If you bring Old Milwaukee to a party, you must drink at least two cans before you start drinking the imported beer in the fridge.
35. Learn to appreciate hangovers. If it was all good times every jackass would be doing it.
Link via: Days That End in Y