It seems more and more people have trouble sleeping, either once in awhile or on a chronic basis. I don't know what the reason is (I'm sure there are varying factors), but I know of a great way to help occasional (like me) or chronic insomnia sufferers.
It's a product called Melatonin, and it can be found in the vitamins section in almost any grocery store, drugstore, or discount department stores (Target, Walmart, Meijer, etc.), and under many brand names. Melatonin is a natural alternative to Tylenol P.M. or products like that, and is non-habit-forming. It's actually a substance that your body already produces on its own, but many people benefit from taking extra to help them sleep.
If you take Melatonin about 20-30 minutes before you want to go to sleep (and relax, of course--don't work out or clean your house after you've taken it!), you will likely begin to feel drowsy, and then sleep is right around the corner. At least, that's been the experience of myself and many others.
Hope this helps somebody out there get a better night's sleep! :)