It’s very true that we all come to a game with a set of assumptions, experiences, patterns of behavior. Sometimes I even find, on approaching a strange game, that I play it by the rules at first, but - without noticing - drift it towards a style of play I know and am comfortable with.

I think a lot can be done in the game text by:
A) being clear about what the game is not about.
“This isn’t about you and your character; it’s not about being one with your character at all. Your character is like a story pawn, something you put in interesting positions so we can all enjoy watching him/her act, talk, think, squirm, choose. Sure, we’ll all feel for the characters. Because of what they mean to the story”.
B) providing examples of play that focus on how it’s supposed to be played.
“John remembers how Liz has been playing Lisa as a snotty, stuck-up girl. He realizes that a meeting between Lisa and the Arch-Villainess would make for a great scene - perhaps the Arch-Villainess will finally lose her temper! So he starts a scene by describing how Lisa is on her way to the temple of the Arch-Villainess with a strange parcel.”
C) giving a few examples of “grey zones” and how to handle them in this particular game.
“At some point, you may feel that you really want your character to succeed at something, even if some of the other players think her failure would work better in this story. That’s okay, the story can wait a little - as long as you don’t totally forget about it. Let your character succeed. She can always fail later, if necessary.”