Go to sleep and wake up at/around the same time every day. No sleeping in or catching up on sleep. Oversleeping is no bueno.
Dont be in front of a screen when trying to go to bed. Light suppresses release of melatonin which is what helps initiate healthy/regular sleep. If you must, consider getting blue light glasses. Blue light suppresses melatonin the most, so you’ll get some sleep benefit(not a ton) by wearing them.
Only use your bed for sex and sleep (seriously) no napping in bed either. No eating, no work, etc. Do NOT lay in bed for more than 20 minutes. If you don’t fall asleep then, get out of bed and relax before attempting to go to sleep. The idea behind this is that it teaches your brain that bed is only for sleep not being awake. Overtime it will allow you to fall asleep and stay asleep easier.
Exercise during the day, preferably earlier to kick start the day. Do not exercise within 3ish hours of bed time. Nutrition is also important. Eating a balanced diet and eating at appropriate times will help you sleep(within an hour of wake up and nothing within 3-4 hours of going to sleep).