The ball moves slowly, so calling it back to use Command: Attack is not ideal. Use Command: Attack to position the ball near the enemy and then simply use it again to harass. This way the ball can hit them easily.
Remember that the ball deals damage to any enemies it passes through, no matter what command it is following. Use this to get multiple harassing passes in quick succession.
Command: Attack provides sight. Use it to check bushes before approaching to prevent ganks.
Command: ShockwaveCommand: Shockwave can create great synergy with all AoE skills, since it flings enemies towards the ball, so if you manage to catch the whole team, they will most likely be flung into the same place, making it a great opportunity to use skills like 安妮的Summon Tibbers
You are squishy without any survivability items, but that doesn't have to be a problem - you can easily keep your distance and order your ball through walls or use it as a shield on your allies (especially tanks).
Orianna has a variety of combos according to the situation.
If you have a team that consists of 3 or more casters, then Abyssal Scepter is also a good choice. A tanky Orianna build with 35-40% cooldown reduction can lead to great survivability and lets you escape quite easy, thanks to Command: ProtectCommand: Protect and Command: Dissonance, while still being able to support your team well.
Since all four of Orianna's abilities can deal AoE damage and scale with ability power, she can also be built as an extremely effective burst mage by putting more emphasis on ability power and magic penetration than cooldown reduction. Builds using Sorcerer's Shoes, Void Staff, and an early Rabadon's Deathcap (as one of your first two or three items) can produce devastating results if you catch three or more enemy champions clumped up, which will happen frequently once teamfights start taking place.