I often have people tell me they have a difficult time relaxing or shutting off their brain when trying to fall asleep. One technique that can be effective to help with this is called progressive muscle relaxation. This exercise is very easy to do and can even be taught to children to help them relax.
Beginning at your toes, take a deep breath in through your nose and squeeze your toes tightly. Breathe all the way into your belly and as you let that breath back out from your nose, relax your toes. Repeat this a few times until your feet feel relaxed. Next, move up to your calves. Take a deep breath in from your nose and clench your calf muscles. Breathe all the way into your belly and as you exhale through your nose, release your calf muscles. Now work up to your thighs. As you take a deep breath in from your nose, squeeze and tighten the muscles in your thighs. As you let the air back out from your nose, relax your thighs. Keep working your way up your body. Next, tighten your abs as you breathe in from your nose, and then let your abs relax as you exhale from your nose. Then clench your fists as you inhale and relax them as you exhale. Finally, squeeze your eyes tight as you inhale and relax them as you exhale.
If you find there is a particular spot that is tense or uncomfortable in your body, spend extra time breathing into that spot. You may have to tense and release that spot a few times before you feel it finally relax.