Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
Personally, I recorded my voice saying “Hey Siri” and set it as the ringtone for my own contact, so when I want to use Siri, I call myself on FaceTime, and as soon as my iPad rings, I can use Siri. That's all there is to it.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.