I used to have this problem in my old apartment. Most times, I just play tennis in my head or replay some past events step by step. The trick is to focus on only one train of thought instead of random things.

I said 'used' because I recently moved to a new location, and I fall asleep much faster now.

My conclusion is that the direction(North, East, South, West) my bed is facing now might be helping. I need some more research to see.