I'll lend you some of my physics texts that I have had to read over the years.
Seriously, what works for me is to clear my mind of *everything*. I try my best to stop thinking when I get into bed. In fact, I try not to think about not thinking when I get into bed. I relax my muscles, and within minutes I'm in lala land. Like someone else mentioned, if I start to think about things while I'm lying there, I will never fall alseep.
That being said, I have never suffered from chronic insomnia, so you may want to see your doctor.