From my own experience, I've read articles and even a famous book about the subject but I've only gone lucid when I didn't try to control it. It just happened. I became aware in the dream that I was dreaming and it's only happened a few times.

I've had moments when I've been on the verge of waking up and was semi-lucid, but only a few times has it occurred in the classic sense within the middle of a dream.