"What's wrong with me?"
the more thin letters we get the more we ask this question. As mine piled up last year I kept asking it and asking it. After they all came back with bad news I spent a long time, money, and effort to improve in every area that I thought might be my weakness. I spent more time narrowing my prospects until I realized that there was only one program for me. I knew it was risky to only apply to one program, especially given that so often the decision has little to do with the student. This year I finally got into the program I wanted and the only things that I'm sure made a difference were my communication with the faculty, and the completion and presentation of my MA thesis. My GRE scores, letter of intent, grades and experience all improved but I didn't ever get much feedback from anyone about it. When I contacted the faculty with a (painstakingly written) email and my MA thesis, they expressed interest. Note that I couldn't have even known what was working if not for the communication. A friend of mine told me that he was in regular weekly communication with his prospective advisor via email right up to the time that he met him in person after being accepted. Not all profs have the time, or interest to chat that much, but if you're worth their time you may benefit from telling them why. I'm no expert at all of this just because I finally got in. I will say, however, that I think communication was a hugely influential factor in my case.