Make sure it's dark. Completely dark. Use blackout curtains or a sleep mask if necessary. Even a small LED light can disturb your sleep. So pay attention!
Ideally, go completely screenless 1 hour before bed. Otherwise, consider investing in blue light blockers. I tested them (read below) and they make a giant difference!
Ideally, your dinner is light and a few hours before you go to sleep. Try to get the bigger amount of calories earlier in the day. Digestion can disturb sleep.
Trouble falling asleep? This breathing exercise might help you calm down: 1) Inhale through the nose to a mental count of four. 2) Hold your breath for a count of seven. 3) Exhale completely through your mouth, with a whoosh sound to a count of eight. Repeat the cycle three more times for a total of four times.