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.
Street football (American)
As in regular American football, each team usually has four downs per series. In order to achieve a series of downs, backyard football requires the team with the ball to complete two passes or reach a certain point on the field. Few games include enough people, or the proper equipment, to run a chain crew to maintain the 10 yard familiar in most organized leagues. These structures encourages passing plays over running, as does the usual lack of offensive and defensive lines. The use of a center is optional, depending on the rules set forth, and other ways to start the play (e.g. the quarterback picking up the ball directly, or holding the ball out prior to starting play, then pulling it back to begin) are often used in lieu of a snap. Play continues until there is a turnover on downs (i.e. the offensive team fails to complete two passes in four downs), an interception occurs, or the team on offense scores a touchdown. Touchdowns are worth 6, 7, or 1 point(s) depending on the rules set out before the game. In some instances, depending on the width of the field more downs are used or teams are given a certain number of downs to score in as opposed to 4 tries to get a first down. For instance, a team might be given 8 tries to score and advance the ball from where they receive the ball or establish position. Also the length of a first down may differ due to the lack of a pass rush. For instance, a team may have to advance fifteen or twenty yards to get a first down in 4 tries.