I got this from the ncaa football rule book:
SECTION 3. Forward Pass
Legal Forward Pass
ARTICLE 1. Team A may make one forward pass during each scrimmage down
before team possession changes, provided the pass is thrown from a point in or
behind the neutral zone.
Illegal Forward Pass
ARTICLE 2. A forward pass is illegal if:
a. It is thrown by a Team A player whose entire body is beyond the neutral
zone when he releases the ball.
b. It is thrown by a Team B player.
c. It is thrown after team possession has changed during the down.
d. It is the second forward pass during the same down.
e. The passer to conserve time throws the ball directly to the ground (1)
after the ball has already touched the ground; or
(2) not immediately after
controlling the ball.
f. The passer to conserve time throws the ball forward into an area where there
is no eligible Team A receiver (A.R. 7-3-2-II-VII).
g. It is thrown from in or behind the neutral zone after a ball carrier has gone
beyond the neutral zone.
PENALTY [a-g]Five yards from the spot of the foul; also loss of down if
by Team A before team possession changes during a scrimmage
down (A.R. 3-4-3-IV and A.R. 7-3-2-II) [S35 and S9].
h. The passer to conserve yardage throws the ball forward into an area where
there is no eligible Team A receiver (A.R. 7-3-2-I).
[Exception: If the passer is or has been outside the tackle box he may throw the
ball so that it crosses or lands beyond the neutral zone or neutral zone extended
(Rule 2-19-3) (A.R. 7-3-2-VIII). This applies only to the player who receives
the snap.]
PENALTYLoss of down at the spot of the foul [S36 and S9].
NCAA Publications - 2011-2012 Football Rule Book (2 Year Publication)