Do join the bandwagon and participate in watching the game. If you're entranced in a show the last thing you want is someone constantly asking you questions about it, right? The game is the most important thing in the room, so watch it and cheer like everyone else.
Do wait until the replay to ask what's going on. Otherwise, remain silent, and go with the flow. You'll pick up the rules as the game progresses. Treat the game as the guy equivalent of The Bachelor season finale. Would you want someone to interrupt every five seconds with silly questions? The answer is a huge no!
Do sit on the sidelines or stand in the back. Especially if you aren't that interested in the game, you should not plant yourself in the middle of the couch if you know you're going to take frequent bathroom breaks or get up for drink refills.
Do dress appropriately, depending on the team that your bar or party is rooting for. It only takes two seconds to research the jersey colors, so save yourself some embarrassment and harassment from zealous fans by wearing the right colors.
Do pace yourself, drink water, and eat lots of chicken wings to offset the day drinking. Emotions are high and the beer is flowing, but keep it classy. You don't want to be the token, belligerent drunk who everyone remembers for screaming obscenities and starting fights.