(I've also had a tendency to sleep-walk occasionally, and to hold a conversation in my sleep which I won't remember when I wake up. At various times this has terrified me - what if I told someone a secret, like about what I got them for Christmas, while asleep? Luckily, sleep-me is discrete so far.)
So, the question in my mind, is how did I get this way? I wasn't always conditioned to sleep so well - in fact, I clearly remember going to my parents aged 10 or so, and asking them "How do I go to sleep? I've forgotten" which confused them greatly. They gave me some good tips, but I was disappointed that there wasn't a formula.
So, my method is to read books. From a really young age I used to read a *lot*. I'm talking about getting a book from the school library, and finishing it in two hours (when quiet reading time had finished, and I was supposed to be doing maths.) After that, I'd get *another* book before we left school, and finish that in the evening. We'd go to Milton Keynes library every other weekend or so, and I'd carefully select 10-20 books (they put up the limit at some point) and finish them before Thursday.
All this time, I'd *always* read when I went to bed. There's a point, though, especially when you're lying down, that your eyes defocus or close, and the book slips from your hand. To start with, my response was to shake it off, prop myself up and carry on reading. But as time went on, I trained myself that when I woke up once after reading, I'd quickly find the book, jam a bookmark in it (if my finger was still in the page) and lie down to sleep.
Later, I got into video games, movies and friends, and didn't have as much time to read. My sleeping during that time was varied, but never awful - I'd have some nights where I couldn't sleep for a long time, but usually I'd drop off. Sometimes I'd read a book, in fact.
Much later still (we're talking maybe a couple of years since I read a book cover-to-cover) at university, I started getting into reading again, and I discovered something crazy - reading made me fall asleep. I'd start reading, and drop off. I've slowly trained myself out of that, but I can still produce the state that it put me in, and fall asleep pretty quickly. If I put my mind to it, I can even sleep badly on a sunny day - I've always been a non-sleeper in daytime.
So my theory is that you can train yourself, by doing a specific thing until you are too tired not to sleep, to not only make that thing a trigger for sleep, but learn to recreate the mental conditions for sleep.
And to read a lot of books!