Forgive me if someone has already mentioned this but making sure your sleep space is a nothing else space helps a lot too.

For me, bedtime was a place for cognitive exercise, wherein I awoke my mind to all the things that required thought, generally speaking a poor idea when your trying to get your mind to slow down. Also now that I'm married it's a place for discussion and other enjoyable activities.

Ideally though, the Bed should be for sleep and sleep alone, no thinking, no reading, etc. If your thinking a lot or feel like reading, maybe do it at your desk until your feeling more drowsy.

Apparently it trains your body to instinctively think it's time for sleep if the environment provided for sleep is consistently exclusive. I have a friend who did this and managed such deep sleep that he could get by on 6 hours a day without need for naps or catch up days.