Heres one that I use all the time and has yet to fail me. When I see a girl eating something in class or where ever just be like "Damn if I had a big ice cold soda on a hot day like this I would share it with you." You can use it for jsut about anythign they are eating. It almsot always cracks them up and they usually offer you some, which could be seen as an IOI in some cases.