any other tips on the writing sample? for those in grad school, how did you choose your sample? any specific comments from the selection committee about why it got you in? did you do revising specifically for the submission? or use something you had already worked over pretty hard and had confidence in? previously published material?
i personally chose my samples based on the page limits, but i wouldn't necessarily do that again if were to apply all over again. there are no hard and fast rules. first priority i feel is the quality of the work. if a piece of writing stands out to you significantly more than others, then that's the one you should use.
on the other hand, i feel like a certain amount of tailoring to programs can be done, as long as an applicant has relatively accurate information. if i were to do it over, i would probably send my most experimental pieces to brown, and my most character-driven work to cornell, for instance. but one should also be careful, because faculties and admissions committees change all the time.
i don't think publication matters that much. it may actually hurt in certain instances, if a committee feels that a writer doesn't have room to grow. i've heard faculty here talking about people here who were accepted based on their perceived potential, over candidates who had more polished work, but that faculty felt weren't as ambitious in their writing goals.
ultimately, i think it comes down to a matter of taste a lot of the time. by the time things get winnowed down, everyone's a fantastic writer and it's just the particular choices of the committee members. i think it's important to remember that humans are making these choices, and humans make many mistakes. so it's all a big crapshoot in the end...