- Call it a trilogy then add books at your own discretion.
- Have a powerless protagonist defeat the strongest possible villain at impossible odds, then invent another situation where a more powerful/malicious/cunning enemy appears.
- Invent some kind of tragedy, ideally make the protagonist an orphan. Alternatively, kill the supportive parental influence causing some sort of downward spiral. The protagonist will then hit rock bottom and run into some sort of epiphany.
- Plenty of adventure, even when unnecessary.
- Villains are not villains, they are morally misguided heroes.
- Include an abundance of conflict and self-doubt. Teen angst is always a hit.
- Follow the cliquey high school stereotypes, to a fault. Use the traditional ‘jock’, ‘nerd’, ‘popular girl’, and ‘bully’. Sometimes you can get away with creating multiple characters following each stereotype. You can put people into clans, factions, divisions, or whatever you want to name the groups.
- Dream up some dystopian future where the world is similar, but changed in a fundamental way.
If all else fails, forbidden love. Happy creative writing!