I think adding a frame will help a lot by attracting the audience's eyes to the subject, however it was not easy for me to find a frame in a frame picture in the school. Since it was the first time I intentionally taking a frame photo so I tend to chose natural frame more than artificial frames because I don't how every work. Although at last I took a photo that I was proud of, it took a lot time to find for a setting that I like an would help to the whole atmosphere. It is very hard for me to say when it would be most useful because I always take photos just to my heart but I think frame in a frame would really help when the photographer want to pull attention to the subject. 
I think natural frame is when nothing is changed intentionally and the picture was took in a setting naturally and artificial frame would be a frame that the photographer added to the picture for example take a photo through a picture frame. 
I would prefer asymmetry more than symmetry because I think photos are a tool that I would use to record the beautiful moments in my daily life so I think symmetry things would be a bit to organized and intended. I think the use of shot would depend on the size of the symmetric object that you are taking a picture of, since mine is a building I chose long shot and cropped out the asymmetric parts.