Jousting: I would always schedule a 5-8 minute time for my middles to joust. This should be short and sweet, the goal is not to jump their legs off. (Maybe not every practice but most). Most teams will have 2 or 3 middles if you have more, great. Have two of them face off at the net, the third one can be the tosser, (or asst, student asst, mgr, etc).
The toss should be a foot or two over the net. The tosser should only be 4-5 feet from the middles and right by the net. A good toss will have half the ball on each side of the net. For some a two handed toss swinging the ball from the waist is most accurate and consistent.
The tosser should have a small cart of balls or handers with balls ready. This should be a relatively fast moving drill. After 8/10 jousts rotate new players in or take a short break if you only have two middles. Make sure that the middles get their hands on the ball and press (sweep is ok but always press) and remind them that the key to winning the joust is that the player that keeps her hands on the ball longest usually wins.
Being good at the joust gives middles a strong sense of "owning" the net. Great middles do own the net and other middles that she faces.