To step aside from the pills previously mentioned as Mary is right, you should try other things first and her ideas were both great. Some other things that are common include:

no caffeine for at least 6 hours before bed time
no smoking for at least 60 minutes before bed time
if you eat before bed try something that is low in sugar if possible
try easy-to-learn relaxation, meditation, or self hypnosis to separate you from anxiety
experiment with white or gray noise such a fan or a radio station between channels or a nature sounds CD on repeat

There are so many options that you can explore.