You must understand that casting such a spell, makes that girl do something against her will. But if you want to know; here is the spell.
1. Form a picture of her in your head, try to hear, feel and see her.
2 If you've got a good feeling of her, go outside and collect sticks, leaves and other natural things.
3 Go to a spiritual place such as a chapel, orbyor house, if you've made your it one of them, and create an amulet.
4 Keep thinking of her!
5 If the amulet is finished, carry it with you.
This doesn't mean that you have to sit back and watch. Try to make contact with her, tell her that you lover her etc.