Running out the clock
In American football, each quarter of a game is measured with a 15-minute game clock, or 12-minute clock in many high school football codes and the German Football League. A team in possession of the lead and the ball will attempt to use up as much of the game clock as possible in order to bring the game to an end more quickly, thus denying the opposition another chance on offense.
Golden goal
The National Football League introduced sudden death during the regular season in the NFL in 1974 and had always had it in its playoffs. Like the NHL, the NFL's rule comes into use at the end of regulation of any regular season game. Until 2011, it applied for playoff games as well. A new "quarter" is started, with a kickoff. Whichever team scores first—either through a field goal or through a touchdown, or far more rarely a safety—wins the game and the game ends. Since in the preseason and regular season, teams are given a "fifth quarter" of 10 minutes to decide the game. Originally if neither team scored after 15 minutes the game ended in a tie. Since the season, each team gets one possession to score, unless one of them scores a touchdown or safety on its first possession. Sudden death rules apply if both teams have had their initial possession and the game remains tied. If after the OT period it remains tied during that time, the game still ends.