Mine was unintentional, I didn't know what lucid dreaming was at the time. I was standing in front of a door and became lucid, spontaneously as far as I remember. I knew if I opened the door I'd go into a dream scene and I could explore it consciously, but I was afraid to because I wasn't sure what to do if there was a nightmare on the other side. I woke up as my hand touched the doorknob.