Choose three to four activities that are calming and screen-free and do them in the same order each evening. Dimming lights an hour before sleep, a warm drink, five minutes of reading, and a brief review of what went well are a complete wind-down sequence.
The most important part is keeping it simple enough to actually do every night. A ten-minute routine done consistently is worth more than an elaborate one skipped when tired. Starting with one change such as no screens thirty minutes before bed is enough to begin improving sleep quality within a week.