This piece for Malachain collects the advice that holds up in practice.
The habits that improve sleep are boring and effective: the same wake-up time every day including weekends, daylight within an hour of waking, no caffeine after early afternoon, and a cool, dark bedroom. Screens are a problem less for the light than for the content, which keeps the mind alert; a paper book or a podcast is a better last hour.
If you lie awake for more than twenty minutes, get up, do something dull in dim light and return when sleepy. Staying in bed teaches the brain that the bed is a place for worrying. Keep this up for three weeks before judging the results, and talk to a doctor if snoring, breathing pauses or persistent daytime exhaustion are part of the picture.
There is more to learn on this subject, and the linked website goes into greater depth. Treat this article as an introduction rather than the final word, and check any important decision against up-to-date, reliable sources before relying on it.
If you try any of these ideas, start small and adjust them to your own situation. What works for one person will not suit everyone, and it is fine to keep only the parts that help. Writing down what you changed, and what happened, makes it much easier to see after a few weeks whether the effort was worthwhile.
The most useful step is usually the first one. Pick a single suggestion, try it for a couple of weeks, and then decide whether it is worth keeping. Small, steady improvements last longer than ambitious plans that are hard to maintain once everyday life gets busy again.