For a max vertical, I love either heavy squats or deadlifts, or even with a trap bar, 75% of your max for an explosive three reps and then drop the weight. Jump as hard as you can. You'll get a couple jumps in there and you'll be like oh my lordy I didn't know I could jump that high LOL
Nothing beats the feeling and energy of tournament play for me. My best volleyball is under that kind of pressure! Fun is always most important to me, but you never know what you're made of until a competitive that atmosphere puts to the test!