Here are the current rules straight from the NFL rulebook
COMPLETED OR INTERCEPTED PASS
Article 3 Completed or Intercepted Pass. A player who makes a catch may advance the ball. A forward pass is complete
(by the offense) or intercepted (by the defense) if a player, who is inbounds:
(a) secures control of the ball in his hands or arms prior to the ball touching the ground; and
(b) touches the ground inbounds with both feet or with any part of his body other than his hands; and
(c) maintains control of the ball long enough, after (a) and (b) have been fulfilled, to enable him to perform any act common to the game (i.e., maintaining control long enough to pitch it, pass it, advance with it, or avoid or ward off an opponent, etc.).
Note 1: It is not necessary that he commit such an act, provided that he maintains control of the ball long enough to do so.
Note 2: If a player has control of the ball, a slight movement of the ball will not be considered a loss of possession. He mustlose control of the ball in order to rule that there has been a loss of possession.
If the player loses the ball while simultaneously touching both feet or any part of his body to the ground, it is not a catch.
Item 1: Player Going to the Ground. If a player goes to the ground in the act of catching a pass (with or without contact by an opponent), he must maintain control of the ball throughout the process of contacting the ground, whether in the field of play or the end zone. If he loses control of the ball, and the ball touches the ground before he regains control, the pass is incomplete. If he regains control prior to the ball touching the ground, the pass is complete.
Item 2: Sideline Catches. If a player goes to the ground out-of-bounds (with or without contact by an opponent) in the process of making a catch at the sideline, he must maintain complete and continuous control of the ball throughout the process of contacting the ground, or the pass is incomplete.
Item 3: End Zone Catches. The requirements for a catch in the end zone are the same as the requirements for a catch in the field of play.
Note: In the field of play, if a catch of a forward pass has been completed, after which contact by a defender causes the ball to become loose before the runner is down by contact, it is a fumble, and the ball remains alive. In the end zone, the same action is a touchdown, since the receiver completed the catch beyond the goal line prior to the loss of possession, and the ball is dead when the catch is completed.
Item 4: Ball Touches Ground. If the ball touches the ground after the player secures control of it, it is a catch, provided that the player continues to maintain control.
Item 5: Simultaneous Catch. If a pass is caught simultaneously by two eligible opponents, and both players retain it, the ball belongs to the passers. It is not a simultaneous catch if a player gains control first and an opponent subsequently gains joint control. If the ball is muffed after simultaneous touching by two such players, all the players of the passing team become eligible to catch the loose ball.
Item 6: Carried Out of Bounds. If a player, who is in possession of the ball, is held up and carried out of bounds by an opponent before both feet or any part of his body other than his hands touches the ground inbounds, it is a completed or intercepted pass.
