Like most 21st century Americans, I battle insomnia from time to time. I personally have no trouble falling asleep. Staying asleep is the challenge. It is certainly true that our minds do not stop functioning during sleep. And I often find myself engaged in some scenario/dream or discussion with myself over some personal or global issues.
The mental 'noise', the incessant thoughts seem to raise my level of consciousness of a nearly awakened state. I know that I am still in a middle ground of consciousness but can open my eyes and stare at the clock radio–its clearly too early to get up.
What I have found helpful is a simple repeatable mantra. If it sounds too simple to work I suggest you have nothing to lose by trying it out.
Simply but silently say, sleep during each in breath. The out breath can remain silent with air being slowly expelled through the nostrils.
This works because it focuses attention on the word sleep rather than any disturbing thoughts. It also signals the brain what state is desired. It gently sets the stage for sleep by blocking everything else from consciousness.
Several years ago I surprised myself by reducing my fear of heights but simply stating the affirmation you are not afraid of heights. Amazingly I was able to approach the edge of a precipice without the usual symptoms of anxiety.
I hesitate to refer to this act as a meditation since meditation is about achieving a wakeful awareness, not sleep.
Still, the power of a simple affirmation can offer insomniacs a meta-physical prescription that can work.