I find routine helps me, my body knows it's getting ready for bed, I don't necessarily go at the same time but I have the same pre-bed routine. I find switching off beforehand helps as well, not going straight from one thing to trying to sleep.
I also make sure my bedroom is just for sleeping (and getting ready etc...) and don't watch TV in there, again part of routine I guess. I had a period of listening to music or Sky News (quite repetitive - if something happens you're screwed though!) which helped me drift off and now am fine without.
I have to have fresh air so make sure the window in my room is open and even have a fan set on timer if needs be.
I find daydreaming can help, let my mind drift to something not too involved which inevitably leads to me dropping off. Interestingly, I do the similar to what Rodge suggests, I can't just stay in bed if I can't sleep, I get up and go downstairs and have a drink and maybe a piece of chocolate then go back up, usually less than 20 minutes but it tends to work well if I'm tossing and turning.
Do be careful on sleeping tablets, I had a very bad period of insomnia some years back and I had to take more than prescribed to get to sleep then found them very hard to come off.