This is just my personal build that works for me. I play the lane as a bi-polar Orianna (Aggressive/Passive) depending on if i know where their jungler is. When I ward Wraiths in the enemy jungle, I ALWAYS throw Q into the enemy brush behind their red, to make sure no one is coming down for a possible engage.

These runes will help early game, as it gives you enough magic resist to sustain against other AP casters, and it gives enough AP to get along with just boots and pots(3). Late game, the runes will only help with the extra 25 will increase, with the Rabadons passive.

I put 9 points in Utility for the Mana regen, and the extra movement speed in addition to the boost of speed from your W. The additional 5% of AP added to basic attacks works well with Orianna's passive, Clockwork Windup, as it will deal even more damage than normal, as you could have expected.

These items help you in all aspects of the game, as it gives you additional mana and mana regen, so if you have an Maokai or mana reliant jungler then you won't be taking as many blue buffs. These items are also effective in the fact that it gives you the ability to nuke the enemy team, causing in complete mayhem for them, especially if you have a J4 jungle, Malphite top, or a MF Attack damage carry. See Team Work for more details.

The reason why I max Q and W first, is for harassment against the opposing lane partner. As for her E, you shouldn't need that till the late game team fights, but it will always be useful for early game if the opposing partner is very aggressive, or if you are low HP and they cast an Ignite on you.

Flash for escape.
Ignite for finishing, Always add a few auto-attacks just for the safety of securing the kill.

Use Q as an option for warding, although it is not temporary, I do suggest grabbing wards just incase you get camper a lot, because why not, you are Orianna.
Also ward enemy wraiths and watch for possible easy kills.

She is a great AP caster, except when you get caught out. Then you are screwed :P
But seriously, try to keep up on MIAs and keep track of their jungler's route as it could help prevent getting caught out.

Take enemy wraiths. If they are not there, then ask your jungler if you can have his. Please ask him before hand. It really pisses them off. Only take a wraith camp when your lane is pushed. Use your q as a way to check the bush to the Right of wraiths (Blue side), or left of wraiths (Purple side).

Combo Orianna's abilities with that of a Jarven IV or a Malphite. Preferably, E the tank/initiator that has a gap closer, and wait for him to be in the fight. Let him be in the middle, and you then can ult the enemy team. Make sure that you have at least one carry in the range of your ultimate.

Check bushes with your Q, it can prevent getting caught out, and it will also help you from facechecking bushes. Although it has a range, try to stay within that range so you don't waste the 45 mana that it cost to cast. AKA Make your spell worth while. Cause you never know, 45 mana could be the difference between a shield and a death.

Try to only use basic attacks, but if needed throw a Q at the target minion to secure the CS. It will waste mana if you only use your abilities for farming. Try to abuse your passive, as it helps deal extra damage from AP.

Orianna can be a great backdoor potential because of the extra damage from her passive. The more AP, faster you can take down those towers! Great for splitpushing, and has a great escape potential because of W speed boost, and masteries.

IF YOU SEE ANNIES BEAR TIBBERS, REPORT IT TO MOBAFIRE, CAUSE I DON'T GET WHY HES HERE!