Having a process preparing for bed helps your body know when it is time for bed.
This means going to bed at the same time every night (and waking up at the same time every morning). Yes, even on the weekends!
You should also have a nightly routine of brushing and flossing your teeth, washing your face, and other nighttime rituals you do in order to get ready for bed.
Having a process that you do every night signals to your body it is time to shutdown and go to sleep soon.