I am making a short horror film tomorrow any tips?

My movie is going to be called The Amulet. The movie is about a group of friends who spend the night at my house and decide to go swimming. While playing a game (not sure what game yet) a girl name ashley will find the amulet and pick it up and call everyone over to look at it. She is then going to put in on and a few minutes later start acting very weird and rude. Basically the amulet is controlling her emotions. Then somewhere in the movie people will die from her then one of the dead people will run out and say ashley is actually acting weird i don't want to do this anymore. She is talking to herself in the bathroom and its really creeping me out. Then she will appear behind me and the girl that are talking about her and say something like Are you talking about me and she will kill everyone and fall to the ground (didn't want to explain the killing) Then at the end everyone will open there eyes.