with a digital camera with a viewscreen on the back (I think they probably all do really)
Sorry for the crudeness of the stick men but I just saw one too many of these self portraits with with camera in shot and it inspired me to do this quick how-to.
This technique has limitations. You can't take a long distance photograph of yourself (because the camera can only be the distance of your outstretched arm). Also, you might not like the way it pushes one of your shoulders forward. And you need the right sort of camera. But for when you just want to take a nice photo of your pretty face / new hairstyle / halloween makeup / etc., it works pretty well :)