Constant repetition is the key to improvement in volleyball. Here are two basic form drills. The demonstrators (11-12 years old) are in their first season of volleyball.
Passing warmup
Tip: Putting her right leg in front helps her with passing on her left knee. As you can see, it would be impossible to pass on her right knee in this position.
Setting warmup
Tip: Tell the young’un to hold her hands above her head as if she were chugging a 2-liter of pop (you’ll get giggles on this one). Oh, and after she releases: Superman pose (notice her arms straight up as if she were to fly to Smallville and save Lois Lane).
Start each practice with form drills like these to help players get used to the feeling of using their hands and forearms correctly in a controlled environment.
20-30 reps oughtta do it.
These are good basic drills teaching proper techniques. I came across this site that I found helpful to explain volleyball technique. http://www.volleyball-training-ground.com