One thing that kept coming up over and over during this long app season, with friends, on forums, even for myself, is CAREER GOALS. Very very important! Only when I updated my career goals did I get accepted from the waitlist.
It seems many applicants spend most of their time and energy on explaining who they are and their past and why this school, but overlook the future and making meaningful and realistic career goals, which may be the most important part. When I updated my goals, they went from being very general and rather broad, to being very very specific, I'm talking specific to the point of company names, programs, and positions.
To get even just a few sentences of detailed career goals required weeks of research, maybe why many overlook it. I read hundreds of pages about my target industry and target specializations within it, I had to speak to many current MBA students in that track, and even spoke to successful executives in that field, etc, etc. Very time-consuming, but VERY important.
By pinning you down to very specific goals, the school can insure that you are a planned person on the path to success. Also, they can lump you into a demographic for their class diversity. So be careful about choosing a goal that is common, as you may place yourself into the most oversubscribed demographic, as a friend who went 0-for-5 did. I have very non-traditional goals (that fit my past and present), but now that I'm in I can take a well-traveled route if I choose.