stand below another person on your team who is in midair and lean back/set. when they land on you, they should bounce back up.

slap/spike a persons hand as they slap/spike yours to high-five them!

this is a pretty well known one but taunting midair makes you do a flip.(taunt with 1, 2, 3, 4 or however it is on controller IDK)

set(lean back) and jump into the ball at the start of a round. it's just another way of serving that I think works pretty well.

spam one of the flip buttons and jump while holding down forward. you can now kinda fly around and it also spikes weirdly well.