Here's a hint. When you don't get the three beeps it's not good form to act like a 2 year old denied thier favorite toy and scream at the checker... GROW UP! LOL!
(I saw a man at LAX Friday just have a melt down because he wasn't selected for precheck. It would have been funny if I hadn't been afraid he was going haul off and start hitting folks and I was right behind him!)