Sometimes referees have difficulties of deciding when the Act of shooting has started. Sometimes players have difficulties understanding when the act of shooting has started. FIBA has made a nice video with explanation. Please be smart and use the terms in the clip if you have some explanation to do. Also be aware of the change in interpretation that was made after they completed the video: if a player passes after being fouled in the act of shooting, the foul is to be considered as made NOT in the act of shooting. High level referees always told me: if you are doubting if it was act of shooting or not (and you should not be, cuz the rules are pretty clear), say yes it was and award the freethrows.