Practice finding defenders and find an open area to tip to based on where the defender is.
Coach tosses a ball high outside.
Outside hitter takes an approach to the net. Defender decides whether to charge the tip or stay deep and cover deep tips. Next person in the line helps outside hitter by telling them whether the defender is deep or short. If the defender is short the outside hitter has to tip over the head of the defender. If the defender is deep then the outside hitter must tip short.