Misunderstood Football (American) Rules
There are a number of rules that fans usually don't understand. What seems to be the most common:
1. Forward Progress
A play ends when a part of the runner's body (except hand, foot) contacts the ground. Or the runner's forward progress is stopped. This is interpreted as when the runner "loses his feet" - when he is not controlling where he is going. So, a runner who is still in control of where he is going isn't considered down by forward progress. But,
Also, the ball is spotted at the forward most point before the runner "loses his feet" - loses control of his motion, not where he ends up after being pulled backwards.
2. Intentional Grounding
A passer may throw the ball away under certain circumstances to avoid being tackled for a loss. This rule is now similar in pro, college, and high school football. The passer must be outside the area where the linemen were at the snap, and the ball must be thrown beyond the line of scrimmage. If the ball is thrown out of bounds, but it passes the line of scrimmage extended out of bounds, it is legal.
Most blocking techniques involve grabbing the jersey. Before it rises to the level of holding... first, the blocker has to be grabbing the defender. The action needs to be at the point of attack - they way the runner is going. The blocker needs to be restricting the defender, the defender is attempting to make a tackle (not moving away from the action), and the restriction causes the defender to miss the chance to tackle the runner. This is usually observed by the defender making an un-athletic move when being held.
4. Field Goal Attempt After Fair Catch or Awarded Fair Catch
When there is a fair catch, or a fair catch is awarded because of kick catching interference, the team with the ball can attempt a field goal, from a kick off position. If successful, it is three points for the team. Very rare to see, but say there's a few seconds left in a close game... the offense punts from their 5 yard line, and the defense executes a fair catch at the 25 yard line. Rather than risking a blocked kick, they can attempt a field goal with the other team ten yards away and nobody can cross the line until the ball is kicked, negating any block of the kick.
5. Blocks In The Back and Below The Waist
There is an area defined usually as about the width of the offensive line and two or three yards on either side of the ball where certain players (lineman who are on the line at the snap) can block in the back or below the waist (from the front). This is a throwback to old school football, but is slowly being removed from the game.
Away from this area, these types of blocking are prohibited in high school football.