This post from the excellent blog-about-vlogs, We Are the Media discusses a technique/phenomenon that I have always found useful ever since Mort Subotnick, one of my composition professors at CalArts, mentioned it to me about 10 years ago.

The idea is that playing someone else your work, whether it's music or film/video, is really helpful, even if they don't say anything. Somehow just sitting there watching/listening to your own work with someone else there gives you a whole different perspective on it.