I have been able to lucid dream for at least the last several years, maybe even more. I don't keep a log so I don't know how often my lucid dreams occur, but I remember my dreams almost every night. They run the gamut from scary and/or disturbing to pleasant or downright joyful. For me, it seems that one of two things happens when I lucid dream. Either my dream is a "rerun," like Technical Ben mentioned, and I can remember that it's a rerun and that alerts me that I'm dreaming, or something about the situation is too out of place, and again, I realize that I have to be dreaming. (But sometimes I dream really oddball stuff and only realize it was a dream after I wake up.) One thing I've done on more than one occasion when I realize I'm dreaming is to make my dream-self start flying, just because I know I can. Sometimes I drift along slowly like an astronaut in zero-g, and other times I've been able to really get moving. In one dream I think I went supersonic, as I watched my home town, then the farm fields below me, flash by in an instant. If I don't like where a dream has been going, flying away from the situation gives me a "reset," most of the time, anyway. There's a lot that you can do in your dream when you know it's just a dream. Myself, I wish I could "unstick" myself from my dreams every night.