I have a few "go to" methods, and in general I find that thinking about things in sequences is especially settling for me:

~"practice" something in your mind. I often mentally review morris dances (!); if I miss or forget a step, I have to start over

~"happy thoughts"...I think about pleasant memories: when my children were born, when I first met my partner, etc.

~ mentally "walking through" familiar places (your childhood home or school, a favourite place you've visited, etc.) step by step, from attic to basement if possible.

I think what happens is that by concentrating on these unstressful, somehat repetitive pictures or ideas, the static of ongoing daytime thoughts, resposnsibilities and concerns are temporarily muted. I also read somewhere that you should institute a mantra along the ines of "my bed is a worry-free zone."

Good luck!

~D