ooh, nice topic rolls_!
I've suffered from what was deemed "chronic insomnia" for about six years now and have striven to find the answer to this question.
First off, you want to avoid alcohol (taken in order to induce sleep). But more importantly, quick-fix sedative-hypnotics, specifically the hypnotic benzodiazepines, wreck the structure of your sleep architecture. I was on Restoril (temazepam) for a long while before it simply stopped inducing sleep; furthermore, it compounded my enormous physical dependence on other prescribed benzos. So it is in your absolute best interest to avoid them like the plague.
As far as vitamins/supplements, GABA and melatonin come to mind. I have used both and although the melatonin didn't at all make me sleepy, every other person I've met who takes it for sleep swears by it whole-heartedly. The GABA supplement is poorly absorbed by the body and has a difficult (impossible?) time crossing the Blood-Brain-Barrier, but it improves Peripheral Nervous System inhibitory activity to some degree. And I have felt this myself. Another like material is Phenibut, which is an incredible and legal supplement that works wonders for relaxation, tranquilization and sleep. I don't know how/if it affects sleep architecture though, I'm sorry.
Herbals? For me, Kava Kava and Valerian Root immediately come to mind; I have them in liquid extract form, and 3 drops of each does indeed get me into more refreshing sleep than if I had taken my current sleeping pill, 0.5mg Halcion (triazolam -
this is what replaced the suddenly ineffective temazepam... another benzo in addition to a rotating schedule of clonazepam, diazepam and alprazolam xr... but I digress

Brewed chamomile tea and smoked damiana, skullcap and/or blue lotus have all helped promote proper sleep stage activity as I sleep, I'm just lazy and haven't ordered any of the herbs and plants. I'd better get on that!!
Hopefully I've given you some suggestions that will help!
I noticed this thread as I searched BL and thought I'd toss a link in here for you in case you were interested:
Any drugs that can force REM sleep?
Peace,
~ vaya