J, if the defense is talking in normal voices about defensive assignments, I will give them the benefit of the doubt.
But if they're yelling (especially right as the shooter is going to release the ball), or if they're gesturing anywhere near the shooter's line of vision, it's a violation.
You can also try to talk them out of it if it's borderline. First time the hands come up, you can say, "Guys, if you distract him, he'll get another freebie." That usually puts a stop to it. If it's obvious, tho, call it right away. That also usually puts a stop to it.
[Edited by ChuckElias on Oct 12th, 2005 at 11:55 AM]