NFL FLAG rules

Starting a possession
Begin at your own 5-yard line.
Moving the ball
Four downs to cross midfield, then three downs to score.
Quarterback running
The player receiving the snap cannot carry the ball across the line of scrimmage directly.
Contact
No tackling, blocking or screening. Defenders pull a flag to end a run.
Touchdown
6 points. A conversion can add 1 or 2 points.
No-run areas
Near midfield and the goal line, use a forward pass across the line of scrimmage.
When play stops
A pulled flag, incomplete pass or out-of-bounds ball-carrier ends the play.