Players stand in pairs across the court from each other. One player has two balls and starts by throwing one ball in the air for the other player to pass back. While this ball is in the air having been passed back, the player throws the other ball to be passed back.
This drill lets players warm up and prepare for passing during defensive and offensive actions. In addition, when two ball are in use reaction time to prepare for another pass is shortened.
New hitters rarely miss because of their arm. They miss because of their feet. Build a reliable approach, then time it with your setter.
When your hitter gets stuffed, five teammates standing and watching is how you lose the point. Good attack coverage turns a blocked ball into a second swing.
Coaches spend hours correcting arms in serve receive when the real fault is almost always the feet. Fix the movement and the platform fixes itself.