I run tryouts as if they're practices.
I think especially in middle school, if you don't use tryouts to teach passing, serving and setting and start work on your offense/defense, then after your tryouts are over, and your first match is right around the corner, then what? Your team will be so unprepared. The first several matches will look chaotic. It's unnecessary! Run tryouts like practice, then you'll be the less chaotic team two weeks later, and that'll create a few extra wins!
Here are the five activities that you should cover each day. (I'm writing the following assuming you'll have a typical middle school team: entirely or considerably made up of rookies. But if your team is full of kids who've already been playing for several years, ignore some of it.)
1) PASSING: Show them how to pass: still arms & use the lower body. No poke, no pray, no flying. Don't forget that the girls can use their hands to serve receive now! So let them try it. But, don't allow them to throw or lift.
2) SERVING: Show them how to underhand serve. Maybe a few girls won't need to. But most will. Many games can be won at the middle school level by merely serving the ball in the court. So let's make sure we can do that.
3) SPIKE APPROACH: Show them a spike approach, but only spend a few minutes a day on it. They can learn it at home if they're motivated to do so. I discovered that chocolate at the end of the week works out great, but only if everyone can properly do a spike approach three consecutive times.
4) OFFENSE/DEFENSE: Go over this about 15 minutes a day. 4-2? 5-1? 6-6? (whoever's in the "3" is the setter! haha) 1 blocker up? (that's what my 14's junior team did for 2 entire years) 3 blockers up? Front row switching? Back row switching also? How about this: 3 contacts? How you play your offense and defense will be decided by the talent level of your girls.
RULE REGARDING OFFENSE & DEFENSE: Don't try to implement what your team cannot execute. You may not have enough time, or they may be too young--whatever the reason, be cautious.
There are many coaches who believe that each stage of volleyball must be used to prepare kids for the NEXT stage. I disagree. Kids should try to master what they're old enough to perform. That gives them the most chance for fun and for success. If they still can't win, well OK, but at least they're not losing because their coach is trying to get them to execute an offense that they were too young to perform.
BE ON THE LOOKOUT FOR POTENTIAL SETTERS: They need to be athletic, hard-working, good attitude, leaders, and quick.
5) COMPETITIONS: Here's where you can really have some fun. Relay race serving, pass to targets etc. They can be timed, or they can last until x number of targets, or, what's GREAT for youngsters, "This drill is over as soon as a team can underhand serve 20 times (not in a row, just 20 total!) without dropping or tossing the ball.
I don't even care where the serve goes." Then two days later, "20 serves in the court, and if you drop or toss, the serve doesn't count." Then a week later, "Your team gets one big point each time an individual can serve three in the court in a row. Eight big points and the drill is over. If you drop/toss, your attempt is over." Similar progressions can also be done with passing, setting, spike approach, etc.
We're still talking about tryouts, huh? Well, after three or four or five days, you can whittle your team down to 10 or 12 or 15, and then continue onward and upward.
TRYOUT ACCOUNTABILITY WARNING: Your principal or AD may force you to keep notes, use a stopwatch, etc. to justify who you keep. But I hope they don't because if you've done what I recommended in Part I, it would be such a waste of time.
Have a great season.