I think it depends on the situation and who you are with(along with how they feel etc). Kissing isn't right if it's all planned out, it should just be allowed to pan out naturally. I'd say ifyou're unsure, you could just give her a little kiss, and if she is into it, then it may progress into something more passionate.
Don't think about it too much, just let it happen.
It depends how realistic the movie is. Some are pretty close to reality, others are way off base.