Lucidity's about awareness. He's got to be skeptical that he could be dreaming at any moment. When people dream, they don't consider the fact that they could be dreaming, and that's what has to change for one to have a lucid dream. In waking life, you have to stop and question whether you're actually awake, and do a reality check.

About third-person lucidity, I've become lucid once but I assumed my own presence in the dream, and didn't remain in the third-person.