the trick to sleeping is not trying to "sleep", even closing your eyes for a time is better than just staying awake and can often lead you into a proper sleep. I normally visualize an animal walk cycle or something repetitive when I'm trying to drift off
Relax your muscles in your head, like you're trying to see inside your skull, and then play word association. But not intentionally. You've gotta try and stop focusing on anything in particular, and especially on things that keep you awake, like things that you enjoy or hate.