Some (but not all) humans experience the autonomic sensory meridian response, a sort of tingling sensation caused by various visual and auditory stimuli. I think it's partly an adaptation to encourage humans to bond through social grooming (removing fleas from hair, etc.). It often causes sleepiness.

So: one thing I've been trying is to use ASMR to make myself go to sleep faster and sleep better, by playing ASMR-inducing sounds through sleep-suitable headphones. I don't know whether this works (planning to measure it sometime) but it definitely feels nice.

To test whether ASMR works on you, and to get ASMR stimuli, go to http://www.reddit.com/r/asmr/top/?sort=top&t=all .

I'm planning to try combining this with periodic audio of someone saying "you are dreaming", as a way of inducing lucid dreams.