For me it was a long process but eventually I got to the point where I fall asleep at the same time and I wake up at the same time. In other words I have a highly predictable sleep schedule. The downside is that I’m not able to sleep past my “wake time”.
Quit smoking and drinking. Nicotine elevates blood pressure and alcohol makes you pass out, not sleep.
Don’t eat anything heavy for few hours before bedtime.
No screens at least one hour before sleeping. This might be controversial because there are different studies regarding the issue but cutting the screen time has another positive effect (see next point).
Reduce or eliminate stimulus - reading polarizing articles, constant notifications, etc.
This one is a personal one - play soft music at a almost hearable level. For reference, I’m a metalhead but I like soft piano/jazz/blues playing when I fall asleep. Set a time to stop the music so it won’t wake you up.
Instead of a standard alarm clock use a sunrise alarm clock. Long story short, it’s a lamp that simulates sunrise by gradually increasing the brightness and the colour of the light.
Use a sleep tracker, for example Apple Watch or any other “smart” watch which tacks your sleep patterns.
This one is a personal one. Just before you fall asleep, e.g. when reading a book and your hand goes down, go to the bathroom before falling asleep, even if it makes you wake up/active for additional 10-15 minutes.
For me it was a long process but eventually I got to the point where I fall asleep at the same time and I wake up at the same time. In other words I have a highly predictable sleep schedule. The downside is that I’m not able to sleep past my “wake time”.