What if Plagarism Happened to Me?

What would I do if plagarism happened to me? I am going to answer this question as a student pretending another student used my work. I would first try to address them personally, making sure not to jump to conclusions. I would ask them if they meant to do it, or they simply forgot to cite it properly. If I were to have to take it any further than that my next step would be to speak with my teacher or other proper authorities. I would hope it would not have to be taken any further than that. I like to believe that others are honest, though that is not always the case. I think it shows bad morals and ethics. How would you handle it? Do you think it would be better to get upset and attack the person, or approach them in a calm manner? I try never to let my patience get the best of me, but working so hard on something just to have somebody come along and take recognition for it has got to be an awful feeling. I would love to hear how you feel you might react in this situation.