Well, I think for your 13th b-day party. You should have a DJ and a pool. Tell all of your friends that are coming to bring their bikinis or stuff like that so that you guys can take a swim in the pool while the DJ is playing some cool music. Some people can dance and some people can swim....or can swim and dance...hehehehehe anyways it should be at night and only invite the friends that you usually hang out with and probably some hot guys that is if you're allowed. Hope I helped.