If I want to wake up early then I have to sleep early, anytime before midnight and I'm up before or around 6am. I will avoid using electronic devices for an hour before I go to bed, I'll read a traditional paper and ink book to relax my eyes, limit caffeine and sugar after 6pm and no food after 8pm.
Having said all that i rarely want or need to be up too early, 8am is perfect most of the time.
"Remove prostitutes from human affairs, and you will unsettle everything because of lusts..."
St Augustine