Keep a consistent schedule regardless of the day. Aka don't sleep in on the weekends to "recover" sleep because it's usually more harmful than helpful.

Don't do anything in bed except sleep and sex. Don't read in bed, browse the internet, watch tv, eat, etc It forms associations of not being asleep while being in bed. The mind is very good at making associations. Force it to make the right ones.

Don't stay in bed if you can't sleep. Basically the same issue as the previous point, but you form negative associations with "trying" to sleep if you lay in bed awake and trying to sleep but being unable. If after 20 or so minutes you can't fall asleep, get up out of bed and out of your room and go do some boring activity and then try again in a bit.

No blue light/very stimulating activity at least 1-2 hours before bed. Blue light disrupts melatonin production which is the thing that helps regulate your sleep-wake cycle. Try to do non-screen based activities or at the very least use some blue light blocking glasses or screen color filters.

Keep a consistent nighttime routine. Create and maintain a routine that signals that it's time to get sleepy and go to bed. Whether it be reading for a while before bed and then brushing your teeth, or maybe drawing and listening to music.

Exercise consistently, but find what time works best for you. Exercise leaves the heart rate elevated for hours afterwards so it can make it difficult for some to fall asleep because they're energized by the exercise. For others, it leaves them so exhausted they basically fall into bed and pass out. Figure out which type you are and stick with it. It's always hard at first but it get's better and you will feel better for so many different reasons.

Avoid alcohol. Alcohol reduces/eliminates the ability to get REM sleep. So you may feel sleepy and fall asleep quickly, you are likely not getting very good quality of sleep.

Experience bright light early in the day. Whether it be sitting next to a window or using a SAD lamp, having bright lights early in the day (within an hour or so of waking) helps regulate the sleep cycle especially when natural light is hard to come by (thanks winter).

Limit caffeine intake, especially in the afternoons. Caffeine has a half life of about 8 hours. So that means if you have an energy drink at 2pm that has 160mg of caffeine, 8 hours later at 10pm you still have about 80mg of caffeine in your system. That's more than a shot of espresso.