1. Characters can not be flat especially foils or antagonist. The popular girls can be stereotypical, but give her a backstory or a reason why. The nerd can be a nerd, just explain it to me. Give me a dynamic round character, not static flat ones.
2. You're OCs must have a distinct personality, they all can't be the same. Make them different, change them up. Don't have Jonathan act like Joan and Frisch.
3. Not related to books in generally, but the PJO and Hoo fandom, I'm sick and tired of daughters of Poseidon named Sophia or Skylar or something that starts with a s. Seriously not to mention having Poseidon break the oath twice, but you're not even coming up with a creative name like Chrystal or Denice.
4. Characters cannot jump from evil to good every second, unless you do it right. A good example would be something like:
"Chrystal stood over her sleeping enemy. One shot. All she needed was to pull back and it would all be over. She raises the gun, but Ana takes control discarding the weapon.
'You can't shoot her.' Ana shouts (only in Chrystal head, though).
'Shut up, he killed Denice, the only one we've ever cared about.' Chrystal replied taking the gun.
'This isn't what she would've wanted.' Ana says putting down the gun. The two fight within Kristin's mind. Shoot or don't. She clutched her head, due to the massive migraine beginning because of another fight."
That sucked, but if I were to read that, I would accept it. I don't want any Darrick's good he helped a baby, but he killed 7 million people just now. He saved 8 million, but he killed another million, that's too confusing. With that said, KB PureLightning out.