I went into a special research about falling asleep faster, and short version,as it was taking me 1-2 hours to fel asleep, there are many rules but the hardest one is to stop all the electronic screens, eating and exercise after 19-20:00, go to bed at 22-22:30 and always, always wake up no later than 6:00. You do this and everything is fine. Kind of self-perpetual habit, as if you always wake up at 6, when you go to sleep at 23-24, you do not sleep enough, so next day you will be tired enough to go at 22. Unless you are in the lucky 4% that got that genetic mutation leting them to sleep only 4-6 hours and be completely fresh.
6 hours is plenty for me and I have no trouble falling asleep - it is just when I go too early (before midnight or 1am), I will wake up a few hours later feeling like I had a good nap, unable to go back to sleep.
However, I used to have trouble falling asleep. The cure for me was think more during the day. :)