Well ideally, you want to watch it in the movie theater by yourself. I actually did that once, and it freaked me out. The movie was "28 Days Later" and the movie was out for a month already, so all my friends saw it already and I had to go at it alone. I'm sure that if I watched the movie with a theater filled with people, I wouldn't have been scared at all. But the fact that I was by myself, I was definitely scared. I also watched it on DVD at my home alone and got the same feeling, but not as intense as watching it in the movies by myself.