Start by doing a quanitified self project. If you don't have a sleep tracker there are apps you can install on your phone that do an okay(ish) job.

Once that is done you can try some tweaking variables:
-Remove TV/Devices from room
-No caffeine after X time or at all
-Read every night before bed
-etc

Some over the counter or prescription medicines may affect sleep. Do not make or take any changes for this project without consulting a physician.