Most teams follow a basic system of tempo passing, with a "4th tempo" ball being high above the net, a "3rd tempo" ball being slightly lower, and a "0" ball being anything under the net.
Coach Marci Allison expanded this tempo system to passing free balls, digging balls, tipped balls, setting and even serves. Have a consistent system throughout skills can simplify skills for players and give them a better sense of the accuracy of their skills and tendencies.