I go through bouts of insomnia and I used to get stressed about not sleeping, which makes it harder to sleep.

My doctor told me (cuz I'm not a pill popper) that just relaxing in bed is enough, so even just lying down and resting will give you enough recuperation to get through another day, so not to worry about it.
That one piece of advice helped tremendously and has shortened my bouts when they do occur.

Then, as someone else posted here, I do two things:
1) Bed is for sleeping (okay, and sex) but it's not for work so no computers, cell phones et al in the bedroom.
2) Wind down before trying to go to sleep. Whether its an hour of TV as it is with my hubby or a few chapters of a book as it is with me, we'll always ensure that there is a relax gap between the end of the day and when we turn the lights off to go to sleep. That helps shut down the brain and move from whirling work thoughts to a steady pace.

Hope that helps!
Mary