they dont tell you anything, if your not selected all you will be told is that. Your OR can try to find out more, but it won't go anywhere. Application "upgrades" are higher ASTB, GPA; to get next month review. Then, in general clubs, community service and anything as a whole big picture will help. Before I appplied again I just kind of said to myself, "how many things can I possibly do to improve my package right now." If you do that you will most likely cover the area that they were looking for. I imagine that is rarely is one single DQing factor, rather small things that ad up. Just do work, think about the standard of a Naval Officer and don't quit.
and cpgillie you deserve +1 for the Summer Heights High avatar.