Sleep is most easily achieved in an atmosphere of total relaxation. So what is needed is to find something that makes you totally relaxed. I usually use breathing technique which appears simple, but of great help. Take in as much air as you can (abdominal breathing) and hold it for a couple of seconds. Then slowly release all the air. You have to watch out for your abdominal movements, and what is important is you should do it not in your bedroom, use another room. Don't use your bed for work, use the bed only for sleep.