one thing i've learned is that as important as it is to be "smart," and know things, it's almost equally (if not more) important "who you know." for every idiot or incompetent fool you've come across in a decent position, and you've asked yourself how the hell they got where they are today, you must remember that they must have known someone, some big shot, who vouched for them. unless you are fortunate enough to be positively selected for by unwritten "equal opportunity," then it's important for you to develop the political prowress to go after what you want. ladies and gentlemen, as we prepare to enter the real world, we must realize that we are entering into a game. you either know how to play or will be left behind.
as i talk to more and more people who have been through the process, it tends to boil down to who you know. many friends have said the breaking point (either in favor or against) their selection into a program rested on a single letter than someone on the committee had read, and had known the person (author of the letter) and called to ask about the applicant. a simple conversation on the phone, and the person had a ticket to a top program. perhaps if it had been a different letter, a name no one had recognized, things would have different.
i don't think you should sweat about not having letters quite yet. but i would strongly recommend lining up your possibilities. drop a line here or there to the people you think could help you out; just to kindly give them a heads up. once most grades are in (around may/june/july), i would start meeting with them, with copies of your transcript, personal statement (maybe), to remind them of who you are and that they promised you a letter. that's what i plan on doing. anyone else have other suggestions? how do people end up finding out which letters were "Strong" or not so strong?