American football
Football games last for a total of 60 minutes in professional and college play and are divided into two-halves of 30 minutes and four-quarters of 15 minutes. High school football games are 48 minutes in length with two-halves of 24 minutes and four-quarters of 12 minutes. The two-halves are separated by a halftime period, and the first and third quarters are also followed by a short break. Prior to the start of the game, the referee and team captains for each team meet at midfield for a coin toss. The visiting team is allowed to call 'heads' or 'tails'; the winner of the toss is allowed to decide between choosing whether to receive or kick off the ball or choosing which goal they want to defend, but they can also defer their choice until the second half. The losing team, unless the winning team decides to defer, is allowed to choose the option the winning team did not select, and receives the option to receive, kick, or select a goal to defend to begin the second half. Most teams choose to receive or defer, because choosing to kick the ball to start the game would allow the other team to choose which goal to defend. Teams switch goals following the first and third quarters. If a down is in progress when a quarter ends, play continues until the down is completed.
American Football Conference
Each AFC team plays the other teams in their respective division twice (home and away) during the regular season, in addition to 10 other games assigned to their schedule by the NFL. Two of these games are assigned on the basis of a particular team's final divisional standing from the previous season. The remaining 8 games are split between the roster of two other NFL divisions. This assignment shifts each year and will follow a standard cycle. Using the 2012 regular season schedule as an example, each team in the AFC West plays against every team in the AFC North and NFC South. In this way, non-divisional competition will be mostly among common opponents – the exception being the two games assigned based on the team's prior-season divisional standing.