I you start treating her like a total jackass, it won't seem real.
The main part is to make it seem natural and unplanned. It will only work if a girl has some interest level in you, in the end it triples it.
Just when you met each other, the interest is usually quite high on both sides. She did not even find out your real self, just likes your exterior and wants to get to know what's inside.
This is the perfect time to get into her head, to make her think about you - this way she'll imagine whatever she wants.
So play hot and cold with the amounts of attention you give her and then after not seeing her awhile, when you are in the hall come up to her and say something like: "oh, what happened to you? You don't even call/visit/come to see me. You should come to place X sometime" and walk away.
Then disappear for a few days from the place X and make her come there a few times. This way she is all confused and is thinking of what YOU think of her, what happened between YOU and her, what will she say to YOU when she sees you at place X, why YOU are not at place X?
Of course I have a friend sitting at place X observing if the target comes in...
Then when I finally am sitting at place X with all my friends around, she comes to me (I have homefield advantage) and says: "I finally found you, I was looking all over. What happened? Did I do something wrong the last time?"
And she is all confused, feels all guilty and you can take her with your bare hands.