When chownah mentioned 'equanimity', I think this was the greatest advice for falling asleep. Falling asleep is the equivalent of simply losing your consciousness; in other words "going unconscious".
So, if your consciousness is quite bright by the time you go to bed, it makes sense that falling asleep is difficult.
'Equanimity' would seem to balance that brightness of consciousness to a 'dimmer' level where 'going unconscious' becomes easier.
If you analyze the process of falling asleep you'll notice these things. If one is approaching their own sleep they might see a few visual hallucinations or hear a few auditory hallucinations before they 'fall'. And 'Hypnagogia' is the stage that people find slightly disturbing in that one feels as if they're descending into non-existence.
The biology of it is quite simple. The release of melatonin from the pineal gland induces the 'unconsciousness' of sleep by shutting off the main functions of the body as it operates on the waking level.
So, this works every time. I use it myself. But not all the time. And this leads to me being sometimes uncertain about the technique. But, that also has to do with the fact that I'm asleep soon after using the technique. Then, in the morning I forget I used it; go to bed at night; and fall to sleep by waiting to fall to sleep.
Most people, I would assume, wait to fall asleep; unless you're talking about people who naturally get very tired at night and just fall off to sleep.
The method is quite simple. It works because of the mechanics and biology of the brain. You can try it your self and notice the effects it has.
So, if you meditate (hold your concentration) on the area sort-of where the pineal gland is you will cause it to excrete melatonin and you will fall asleep. It's pretty simple. I think a lot of people grow up being afraid of that 'Hypnagogia', and develop a sleeping strategy that entails 30 minutes, and hour, or more of waiting to fall asleep. The reality is, you can simply induce sleep on your own.
To some people, this will sound simply unnatural. People regard sleep as an unconscious process. Well. yes, it is when you finally are asleep. But in order to fall asleep you must, in one way or another, face the Hypnagogia which will come between waking and sleeping. This stasis is mediated by melatonin. It is pretty normal in my opinion to stop wasting one's time waiting for one's own wound-up psyche to release enough melatonin in order to fall asleep, when you can just rush your brain with it on your own - and you're off to the races.
As I started using the technique I began to become more comfortable with Hypnagogia. I am still not as comfortable (with it) as some people I know. These people embrace Hypnagogia like it was a death wish. To their advantage, I must admit, they are asleep by the time their heads hit the pillow.
'The currents in the world that flow, Ajita,'
said the Blessed One,
'Are stemmed by means of mindfulness;
Restraint of currents I proclaim,
By understanding they are dammed' (Sn.1035)