I know there are quite a few apps on the apple store. and probably for the stores for other devices as well...
then there are brainwaves that are thought to help with sleep(and other things) . some people have found these to work, while others haven't.

I know that drinking a 2 litter of doctor pepper right before bed as a 14 year old, doesn't cause lucid dreams as i was instructed that it would the night before i actually consumed the whole 2 litter right before bed (i'll just say it kept me up all night, and i was constantly running to the bathroom. lol!).

medications can also play a part in it. even more than just the ones that speciffically are for sleep. other medications can affect sleep , such as cymbalta.. when i was first on it, i had constant lucid dreams, although it got tiring and i would wake up ready to fall right back to sleep after a nights sleep.
also with seroquil it is for sleep (the reason why i'm on it), but when it does kick in, the first 3 hours i'm out.. like.. comatose kind of out.. NOTHING wakes me up.. i still breathe, but no type of sounds, or volume of sounds or stimulation like opening my eyes forceably or picking my arm/hand up, none of that will wake me. and otherwise i'm super senstive to sounds, and the volumes of it.