[Ref in PA]

This is what I look for:

If the foul is from behind, and there is not chance to block the shot cleanly, more than likely that will be an intentional foul. If a player is beat and the only way to get to the ball is to go through the player, then the defensive player has no legal play on the ball. If the defensive player is fouling just to stop the shot and not play the ball, you will get the intention foul called.

If the defensive player has adequate position (but not to take a charge) then a foul on the arm stopping the shot will result in just two shots, not an intentional. Fouls that play the man instead of the ball risk being called intentional and possibly flagrant - depending on the severity of the foul.