Here's a little 'home remedy' of mine for how to cure insomnia. I don't mean serious long last insomnia (unfortunately) but this little 'cure' of mine will hopefully help you during those nights when, no matter what you do, you can't get to sleep and you don't know why. This 'cure' has been mocked by a few people I know, but it has worked for me a couple of times and will hopefully work for you too.
So anyway, when you're lying in bed tossing and turning and you can't dose off, I suggest you hold your breath. It sounds silly, but just hold your breath for as long as you can. When you start breathing again you'll be quite out of breath and also much more susceptible to falling asleep. For me, doing this has taken me from the annoying non-tiredness of sleepless nights to the feeling of getting to the bed after a long day. I hope this is useful to somebody!