Ten

If you're writing canon characters, make sure you know their character well enough.

Movie fanfictions are a hell yes, as long as you don't twist the movie plot to make it sound like its isn't even that movie any more.

I personally don't know too much the Vampire Diaries, but from my knowledge, vampires there need their damn ring to not but up in the sun.

People are not naturally born with purple hair.

The idea of falling into you favourite book is overused. (Yes I'm a hypocrite.)