Suspense is a difficult thing to achieve in film. Alfred Hitchcock said that suspense means letting the audience know more than the characters. However, while Hitchcock's definition is very well put into words, suspense is much more than that.
To make suspense in films, you have to grab the viewer's full attention and you have to create interesting situations which feel plausible and whose outcome is hard to guess. But more than all, to get a viewer to feel the suspense, you have to make him care about the characters he watches on screen.
In other words, you can't feel anxious about something or someone you don't care about. This is why many of the so-called suspense films fail. They have the best of ideas but directors forget that, first of all, you have to let the audience be invested with the characters
