When to raise the offside flag

[BoomerSooner]

As Tuss said it depends on if the player in the offside position was actively involved in the play. Being in an offside position is by no means an offside violation, however once the ball is played to such a player the flag should go up and the AR should hold his mark to make sure the proper restart point is known to all.

If the offside player were to retreat immediately seeing that he is in an offside position (never makes an attempt on the ball) and no advantage is gained by his being in that position, do not signal offside and the ball is fair game for all.

One big key from my experience with other referees is that the benefit of the doubt concerning advantage should be given to the defense (i.e. player offside, ball played ahead, offside player makes doesn't make any attempt to give chase, however a defender gets picked by him standing watching the other attackers give chase - offside and flag in the air)