I've tried loads of things over the years, they all seem to work for a while then I'm back to square one
several have already been said
No tv/phone/laptop right before bed, kindle or a book just for a little while
Don't lie in on your day off or stay up stupidly late on your Friday night. Stick to a schedule
Lying awake? Get up, read for a few. Try again.
Keep the bedroom for sleeping
it's not for watching movies or aerobics. Your brain should associate the bedroom with sleeping
Warm feet and fresh air is a must for me. We have a thicker duvet and throw on the bed so I can have the window open without him freezing!
Breathing exercises? Breathe in for 8, hold for 4, release for 4. Or whatever numbers you can manage
Breathe in, as you breathe out imagine pushing it out to your feet, the next breath to your ankles, then calves etc all the way through your body until either you're asleep or you're at least relaxed
Medication/aromatherapy oils/white noise
Fitbit or similar phone app that monitors your sleep. We discovered we both woke up at a certain time of the morning in a rather odd pattern from it and it was nextdoor slamming his car door going to work the 3am shift!!