The simple tapping of :s-square: .
But here, it's the timing that matters.
To do an overhead volley, tap :s-square: when the ball is hovering around player's head, & his back is towards the goal.
For side volley, tap :s-square: when ball is a reasonable distance beside the player's legs. (might sound little complicated)
For a regular volley (normal volley straight), just tap :s-square: when the ball is around knee height.
Remember, just tap, otherwise it's skyward.
Hope that helps.