"Try it and you'll find out"

[BktBallRef]

I always tell the thrower that it's a spot throw-in. I also warn the defender not to break the plane. I consider this to be preventive officiating. I can't remember the last spot violation or plane warning I had. i think both are a result of a few words.

But I think this is different than the original topic. I don't tell the player that he can throw into the BC. I don't tell him he can't throw into the goal. I don't tell him he can call TO if he can't pass the ball in.

IMO, those duties belong to the coach.