I find that Progressive Muscle Relaxation helps a lot because it both focuses your mind and gives you a subtle work out while never leaving the bed.
You don't need a formal program, just work your way either up or down your body one small muscle group at a time, doing each one twice before moving onto the next. Examples are: point your toes, pull your toes up, press your heel into the bed, squeeze your butt together, tense your stomach muscles, make a fist with each hand, press your elbows into the bed, pull you shoulders up, push your shoulders down, raise your chin to your chest, take a deep breath and hold it before letting it out, smile hard with your mouth closed, pucker your lips hard, squeeze your eyes shut, raise your eyebrows. Do everything as hard as possible and hold for a few seconds while saying "tense" to yourself, then "relax" when you let it go. After about 15 minutes of that, I find I'm much more relaxed.
I also sometimes use some nature CDs I have - birdsong, water sounds etc. I usually fall asleep before it's finished.