Command: Protect can be used on yourself to return the ball back to you quickly. Combine this with Command: Attack for a quick harassment.
Command: Dissonance is a very powerful escape tool if Orianna has the ball. The combination of speed and leaving a slowing obstacle can be quite powerful.
Command: Shockwave can be used to drag enemies towards you or away from you if you position the ball properly.
Orianna can only affect the area the ball is around. Use this to your advantage.
Watch out for Orianna's ball returning to her due to leashing. This may cause some unexpected situations.