The things that I have found that work for me in falling asleep:
1. Exercise. A long walk for an arobic work out in the evenings with 1.5 to 2 hours to cool down. If I exercise too close to the time I want to go to sleep, I have too much energy. It also helps with aches and pains of lying in bed. I suspect this is more of an issue for those of us over 40.
2. Melatonin. Only take it just before your normal sleep time. If you wake in the middle of the night and then take it, you may end up badly depressed the next morning.
3. A glass of wine or a beer. In moderation, alcohol is good, but too much can cause sleeplessness so if you tend to over indulge, this is a bad idea.
4. Counting sheep (or lobsters, or hippopotami or whatever) The point here is to break the obsessive thinking and bore yourself into sleep. I've had a hard time keeping my concentration on the task and I find this rarely works.
5. Rain or wave sounds. I have some MP3 files of rain that helps a lot. Not always, but often enough that I strongly recommend it.
6. Reading. "The Decline and Fall of the Roman Empire" should just about do it. The mild eye strain I get if I read without glasses might sometimes help.
7. Listening to podcasts (or the radio) If I listen to podcasts that I am familiar with and that have a consistant program format ("Wait, Wait, Don't Tell Me" or "Car Talk" etc) despite enjoying these shows, I find they sometimes help me go to sleep. If the show is unfimilliar to me I tend to pay closer attention and this keeps me awake.
My issues with sleep are much like what others have mentioned above. In my 20's it took anywhere from 45 minutes to 3 hours of lying in bed before I fell asleep. Now at 45, I usually fall asleep fairly quickly, but then again, I also exercise regularly whereas when I was younger, I never exercised.
I suspect exercise is a major key to getting good sleep. It doesn't need to be much. A walk in the evenings after eating, a jog, or a work out on an aerobic machine, regular bike rides. Whenever I slack off of exercising, my sleeping suffers.
Lars
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Never let the weeds get higher than the garden,
Always keep a sapphire in your mind.
(Tom Waits "Get Behind the Mule")