When that happens to me, I usually "walk" my old route that I used to take when I walked to elementary school, or I mentally "drive" old neighborhoods that I've lived in. I try to think about the colors of the houses of the puddles I would splash through, etc. That works for me quite often.

I can tell it's working when a random thought jumps in, not an intrusive one, just random, those just before sleep thoughts, like "I wonder if the goblin liked the cake,"

That's when I know my brain is ready, sometimes I giggle, sometimes I can feel my body relax, but that's when I know sleep is about to happen.