flatten out your leading hand. Bend your second hand at a right angle, then tap it against the middle of the palm of your first hand.
Dads will find this similar to a timeout signal, but note there are two important differences. First the moving hand is bent at a right angle, not straight like in a time-out. Second, making the again sign will not allow a three minute cessation of all activity, wherein you may gather additional alcoholic beverages and salt laden nibbletts.