I've struggled with insomnia all my life too and have relied on pills, marijuana, etc. to be able to sleep. I am now using diphenhydramine (Benadryl) which I feel is better than what I've used in the past but my goal is to be able to sleep without help at some point.
Some things that have helped me in the past include what story suggested, staying away from anything stimulating, including television, computer, etc. for at least a half hour before bedtime. Also, your sleeping area should be used only for sleep (or sex if that's applicable) and should not be a place where anything else is done, including reading. Keeping that space cool and dark can really help, too.
When I wasn't able to sleep for several weeks what finally cracked it was moving into another room. Doing that took the pressure off of my mind because my bed/room had been associated with insomnia for too long. I told myself I am just lying here (here was my living room floor) and I don't have to sleep. Somehow that finally broke the spell of insomnia.
I've also used supplements and herbs like magnesium, calcium, skullcap, hops, passionflower. I know a lot of people like melatonin which is a hormone our bodies naturally produce to induce sleep. Valerian is another herb people find success with however some people, myself included, get a paradoxical reaction and actually get wired from it. With any of these, seek advice from an trained Herbalist or Naturopath, both of whom rely on non-drug methods of medicine.
I agree with Dee that relying on marijuana, even if medical, may wind up hurting you more in the long run. If you can avoid it it would probably help you more. And his idea of a sleep clinic is a sound one. I will be trying that myself when I can set it up.
Take care.