Maintain the 12-15 yard distance between you and the QB. When he drops back, so do you, otherwise he'll make a sudden turn and you'll be in the middle of the play. (this is my toughest challenge)
Box-in - keep the play surrounded by officials. You have a wing to one side, umpire on the other side, back judge in front - so make sure you stay in a position behind the play to complete the box.
Did someone say slow down? Well, slow down some more. 🙂
When giving signals, pretend you're on TV. Slow (no, slower), verbalize your call just like you're on TV, that will force you to slow down - plus it forces you to think of the enforcement.
Don't stare! Keep your head on a swivel and your eyes moving. From that position, it's easy to get tunnel vision.