I was once told there were two types of insomnia, sleep acquisition (can't fall asleep) and sleep inhibition (can't stay asleep). Luckily I usually only have one kind, can't fall asleep. So I was asked how I fall asleep. I've listed before some of what works for me.
My friend Alison said she would take 0.5 mg of melatonin when she couldn't fall asleep, followed by a second dose 30 minutes later if she still weren't asleep, and that always worked for her. That never worked for me, so I gave her the rest of my bottle. Then I learned that melatonin is released when your eyelids don't have any light on them, so I tried the eye shield, and that has worked well for me. As it turns out, the proper dose is 0.3 mg of melatonin instead. Melatonin is also effective for insomnia in ADHD children!
White noise is my other major aid along with an eye shield. However, I've also considered listening to an audiobook or podcast as I fall asleep. (Interesting note about working memory and falling asleep, sounds like it would also be effective for me.)
Other tactics ... I try to switch off multi-tasking (thinking about everything) by concentrating on something, like the white noise, or my breathing if I have no congestion to distract me. If focus doesn't work then I think about thinking about nothing until my mind is clear.
I like to do static stretches before bed and when I can't sleep. It runs off some energy, and it aligns my body. Then I climb into bed, making sure that I'm super-comfy with no pain points, all symmetric joints aligned, and no twists.