In many horror movies, a possessed person is shown spinning his/her head through 360 degrees. How are those scenes shot in the movie?
They used a dummy to film that scene. They created a robotic head that looks like that girl. It can move its head completely 360 degrees. It can also move its eyes and mouth and exhale warm breath. They put this dummy at place of girl and shot that scene. Here is a link to YouTube video of behind the scene.