I'm not a healthcare professional, just a mom who was looking for ideas to help her child who was struggling with chronic insomnia. I asked around in wellness forums for suggestions, and thought it might be helpful to compile and post them here. Not everything will be useful for every case, but it gives you enough ideas that surely some combination will help the sufferer get relief.

• limit heavy foods after 8
• wear blue light glasses for evening screen time use, and then put away screens 1-2 hrs before bed
• red light therapy - when the sun sets, use candlelight or red incandescent bulbs
• magnesium in various forms, oil or lotion on skin, mag glycinate or threonate
• if you have acid reflux, take activated charcoal capsules before bed
• white noise, fan
• dark room, blackout curtains
• addressing stress levels via prayer and relaxation techniques
• weighted blanket
• heating pad over chest
• chamomile tea and other herbal blends with lavender, lemon balm, etc. Steep for at least 20mins
• cod liver oil
• at least 45 minutes of exercise every day, heavy exertion
• listening to a podcast, audiobook or lecture 
• reading an hour before bedtime, nonfiction so you don't get caught up in the story
• calcium deficiency - 1000mg to 1500mg daily
• CBD oil orally or used in a cream, I put it on my lower spine and bottom of feet
• drink glass of raw milk at bedtime
• eating cold butter before bed
• drinking tart cherry juice
• journaling emotions and stresses on paper to get it out of your head
• repeating a phrase or a section of memorized verse, praying the Lord's prayer
• essential oil blends, rolled on skin or diffused in room (I like Sleep Envy which contains Copaiba, Lavandin, Sweet Marjoram, Chamomile, Geranium and Valerian.)
• homeopathic coffea cruda for mental hyperactivity
• look into supplementing with nervine or adaptogenic herbs, learn more here
• turn on a background ambience video for settling down, I love this gentle rain on tent scene