I had lucid dreams fairly regularly during my teen years (I suspect due to some strangeness caused by sleep apnea). These days it's treated and I don't have these anymore. Though, for anyone interested I think it's totally worth trying to trigger it. It's an interesting experience.
I had lucid dreams as a teenager too, and completely forgot about it. Then about a year ago it happened again - and I remembered how cool it was.
I find I can nearly always do it if I wake up in the middle of the night then just think about it as I fall back asleep. I guess my subconscious then keeps a look out for weird stuff... "That elephant wasn't there when I looked a minute ago. Wait, elephant?! I'm dreaming!" Then it's flying time.
Lucid dreams for me were a side effect of other things. They didn't effect the quality of my sleep, which was already very poor.
My sleep apnea was such that my brain "woke up" about 45 times an hour. This kept me from ever experiencing full REM cycles. One of the more jarring side effects is that, unlike other folks, I when I went to sleep I dropped from wakefullness directly into REM sleep without anything in the middle. This meant I would start dreaming immediately. I was able to remember extremely vivid dreams when someone would wake up up about 5 minutes after I'd fallen asleep (sometimes less). This slowly allowed me to realize I was dreaming after I'd fallen into this "fast REM" sleep.
Thankfully, the sleep apnea is treated now and I no longer suffer the somewhat debilitating side effects of not getting REM sleep. For me those side effects were constant drowsiness, inability to focus, falling asleep while driving (smashed into someone at 75mph at 3 in the afternoon because of sleep apnea thankfully my car was lower than theirs and I just slid under them and smashed up my hood), irritability, etc.
This is way off topic but anyone who thinks they might have sleep apnea should totally get checked out. There has been a huge quality of life change for me since getting this treated.
