I have a very hard time trying to mentally relax, and I can't get good sleep if I have a lot of things stressing me out. I'm usually falling asleep because of exhaustion from my week of working 50 hours plus whatever grading and lesson planning that I have to get done, and that leaves me waking up in the morning just as tired as when I went to sleep. The only time that I really get good, restful sleep is when I've been able to catch up on everything and take some time to relax... which is a rarity as something always seems to need to be done all around me.
When I was in middle school, I got into the habit of listening to talk radio to pass the time falling asleep. It started out as being a way to both tune out my parents arguments at night as well as entertain me when I couldn't sleep. As I got older in high school and in college, and as I started to have stress induced insomnia, I'd usually lay awake listening to some sort of news or comedy or old timey radio theater to try and quiet my mind. Sometimes it worked, and sometimes it wouldn't. But because I've always fallen asleep with the radio on as a distraction from my thoughts or as background noise, I have a very hard time falling asleep without something to listen to.
I go through phases in what I listen to and like I said, I listen to a whole bunch of different types of programming when falling asleep. I've recently been listening to a lot of Coast to Coast AM and Ground Zero for whatever reason. I'm not close to being a believer in the paranormal or in conspiracy theories, but it's entertaining to listen to and to expose myself to different ideas.
So yeah. The two things that help me get good sleep are having a clear mind and having the radio on. I also get weirdly calm during storms and high wind, and that helps sometimes as well.