OK, here's what I do. I imagine I'm in Coronation Street. I mentally walk down the street naming who lives in each house. I'm always asleep before I reach the corner shop.
Yes - I can usually sleep anywhere, anytime, and often do.... however on those occasions when I can't, I seem not to nod off all night. Sometimes I could sleep all day, given half the chance...
I;ve tried all sorts the best one is making sure my bedroom and my bed look really comfy and inviting, get into bed then snuggle down, think about being on an icebound boat shivering with cold or fighting your way through a rain or snowstorm, anything like that which you can remember feeling cold wet tired gets me off after a while, Try not to think about Not being sleepy.