Another problem players demonstrate on the foul line, especially in game-deciding situations, is inappropriate shot speed. Players need to shoot at their normal speed, not slow down the shooting motion for extra care. I've seen many teams at both the high school, college, and pro level lose games because the coach told the players to slow down, to be extra careful. What you need to say is, prepare for the shot carefully, but shoot at your normal speed. In a game, a player usually shoots two shots at a time under pressure after sprinting up and down the court.
Sensible practice involves shooting under the same conditions.
Instruct your players to shoot two shots and then sprint down the court several times while dribbling the ball. Repeat this shooting and sprinting as many times as needed to duplicate game conditions. If the entire team is doing this drill, the center position on the foul line will probably be taken. Instruct players to shoot from any position on the foul line or even the foul line extended. Of course if you have the luxury of six baskets, use them.