Fifteen

If your character has a pet, you can't forget about it halfway through the fic.

Eyes can be of colours other the 'bright blue' and 'emerald green'.

If you write a 200-word essay on your character's love interest's eyes, you're doing it wrong.

Not all females cut bangs, and not all men have short, shaggy hair.

You can't create a character who reads a lot and is very informed about stories and classics and wonderful things, but hasn't heard of Lord of the Flies.