Habits
Consistent sleep schedule: wake up at around the same time, regardless of when you go to sleep
Wind down before bed: avoid mentally/physically taxing, aggravating, or exhausting. Avoid working out late in the evening. Avoid doing work, reading aggravating news, etc. for ~2 hours prior to going to bed. Focus on relaxing activities (e.g., reading a book, watching passive TV, taking a bath, meditating, yoga)
Avoid eating before bed: stop eating ~2-3 hours before bed. Drink water ~1 hour before bed
Avoid caffeine after noon: avoid drinking caffeine for first 90 minutes after waking up, and drinking caffeine after noon
Avoid alcohol, especially at night: alcohol negatively impacts quality of sleep
Exercise regularly: attempt to do ~15-20 minutes of cardio per day, with target heart rate in 130-140 bpm range
Develop a bedtime routine and habits: develop a ~15 minute routine before bedtime that helps your body know that it's time for sleep (e.g., stretches/yoga, skin routine, lowering temperature, cleaning up kitchen, etc.)
Monitor your sleep quality: use sleep-tracking fitness bands to track total time asleep, quality of sleep, sleep debt, and to identify potential impediments to sleep
Practice muscle relaxation and breathing techniques: practice consciously relaxing the muslces in your body starting at one end and going to the other. Try breathing exercises (e.g., 4-4-4 one where you breathe in, hold, and breathe out in 4 second increments) to help relax your body
Get natural sunlight in your eyes and on your skin early in the morning: within first 90 minutes of waking up, go for a walk or get natural sunlight in your eyes/on your skin for 10-15 minutes (ideally not through a window). This helps maintain circadian rhythm
Avoid lounging in bed: limit time spent in the bed to going to sleep and getting up, and avoid lounging in bed while watching TV, being on the phone, etc.
Have "bed clothing" that you only wear to bed: have pajamas or outfit that you only wear in bed, and don't use throughout the house, for exercising, etc.
Limit bright screen time before bed: avoid screens right before bed, and if you do use screens, make sure that blue-light filters are on, and screen brightness is as low as possible, to avoid the waking-up effect of blue light and bright screens. There are ways to reduce blue light on computers (such as f.lux software) and reduce iPhone brightness beyond the lowest setting (through Reduce White Point feature)
Use alarms that align to your sleep cycles and wake you up during light sleep: use alarms that sync with fitness bands that track sleep cycles, to make sure you are woken up during light sleep, and not abruptly during deeper sleep stages. Apps can monitor your sleep stages and wake you up in 15-20 minute "alarm" ranges to make sure you are not woken up during deeper stage of sleep (which is more disruptive). If not using an app, consider not using loud alarms, and instead use very quiet alarms that only wake you up during light sleep (e.g., vibration-only alarms, set 15-20 minutes apart, where it is not likely to wake you up during deep sleep)
Environment
Create a dark environment: make bedroom dark during sleeping time (if overlaps with sunrise, use blackout curtains)
Lower temperature: keep temperature in the bedroom lower than normal house temperature (e.g., if house is 70 F, have bedroom at night at 62-67 F)
Find mattress, pillows, sheets, and comforter that works for you: figure out the perfect combination and type of mattress, pillows, sheets, and comforter that helps you fall asleep fast, reduce disturbances during the night, and help you feel refreshed in the morning
Find your sleep position: experiment with different sleep positions to find what is the most comfortable for falling asleep and staying asleep. Train your body to be in that position whenever you feel that you are falling asleep, so in the future, it will be easier to fall asleep once you get in that position
Try weighted blankets: try using different weighted blankets (different weights) to see if it improves sleep quality (weighted blankets vary from ~15lb to 35lb)
Use noise, if needed: use white noise machine, background tv, music, sleep apps (with bedtime stories), or other sounds that help you fall asleep and stay asleep
Keep sleep environment clean: change bedsheets at least once a week. More often if you don't shower before bed
Experiment with bedroom scents: try using wall plugs or other scent-producing items that can help establish bedtime scents that can help going to sleep (e.g., lavender and chamomile scents could help with relaxation)
Have calming colors in the bedroom: have calming colors and décor in the bedroom that are conducive to relaxation
When sleeping with a spouse, consider getting a larger bed and/or separate blankets: consider upgrading to Queen or King size bed, and/or getting separate blankets if being in bed with a spouse leads to frequent sleep interruptions
Use sleeping mask: use sleeping mask if room gets too light during the sleeping period
Use earplugs: if noise disrupts sleep and is unavoidable, use earplugs
Resolve Issues
Resolve any breathing issues you may have: see a doctor if you have sleep apnea, snore, have restless leg syndrome, or any other medical issues that interfere with sleep
Manage overall stress: focus on mindfulness and reducing overall stress in your life, if stress/anxiety is contributing to poor sleep quality
Keep a sleep diary: track daily activities, foods, amount and timing of exercise, social engagement, general mood, and other factors that may be influencing your sleep quality
Try sleep supplements, if needed: try melatonin, magnesium, and other sleep supplements if nothing else is working