difficult to know what is the right moment to start the approach. it might be frustrating because sometimes you leave too early, sometimes too late.
a good general rule to get a correct timing is to place your right foot on the ground when the setter touches the ball.
after that you just take you step 2 with your left foot, and set up the plant (steps 3 and 4 next to each other) and take off to the air.
in the air focus on reaching high and making a good contact to the ball.
the control beats the power when learning volleyball spike.
repeating one controlled swing after another makes your spike more and 