My ex-girlfriend could (she said) induce lucid dreams as well. (We also once shared a dream... not a lucid one, but we woke up and she was telling me her dream, and it was the same one I just had...)
I've only had one lucid dream that I can remember. It was fascinating: I suddenly realized I was dreaming and I could do whatever I wanted to do. So I decided to fly. (I love flying in dreams, it's like a great gift when I get those dreams). I flew up but there was a cieling above me and my head got stuck in something like a grate and I couldn't go any further. I thought to myself "ah-ha, I know what's happening, my sleeping physical body has been moving around, and my head is banging against the head of the bed. I'm gonna wake up now." I decided to wake up, did, and sure enough my head was jammed into the board at the head of the bed. I then got up and went to get a glass of juice. I floated down the stairs to get the glass of juice and talked with a cousin of mine who lives thousands of miles away, but was hanging out in the kitchen. A bit later, I "really" woke up.
Or did I?