What I try to do is aim for relaxation, rather than sleep. Otherwise I start getting anxious that I'm not asleep yet.
Breathing exercises can help. I've also recently started doing sit-ups before bed and I find that helps tire me out, even though my blood is pumping afterwards.
Pitch darkness is a prerequisite for me, and I leave my phone outside the bedroom.
If none of this works, then there are herbal-based remedies that actually work. I won't mention any here as I don't really like the idea of promoting this option, but a simple internet search should bring a few up.
Always go with a trusted brand or speak to a doctor for recommendations.