1) Players alternate sliding full beer cans back and forth across the table.
2) 3 possible outcomes occur:
a. The beer can falls short. Nothing happens.
b. The beer can falls over the edge. The other player must CATCH IT (this takes minimal coordination, but you'd be surprised how clumsy some people are). If you don't catch it, someone will probably have beer explode in his/her face later.
c. The beer can hangs over the edge. That is, if you get under the edge and can see can bottom, it counts. In this case, the other player must DRINK IT. All of it. Then get a new beer can to play with.
NOTE: The drinking player must open the can no more than one foot from his/her face. If the can has been dropped, the explosion can get ugly.
3) The other player/team gets a chance to slide the beer can across the table.
This is a fast-moving game. Generally the can is slid every 5 seconds or so. You also consume a good amount of beer in not much time, so 30 mins or so of this game makes for a great pre-party activity. If 4 players play you can slide either one or two cans at a time. An expert variation is to play with bottles...just make sure you have a soft floor in this case.