I'm re-applying to several of my top choice graduate programs (comp. lit. programs in the U.S., specifically) after being rejected last year. I'm making some substantial improvements to my application materials (writing samples, personal statements, etc.) and applying with a somewhat different and more clearly articulated focus. From other posts I've gathered that re-applying to a program doesn't necessarily lower chances of admission. However, how advisable/appropriate is it to acknowledge the prior rejection while re-applying? What about contacting the department as to what the weakness were in the prior application - is that advisable, or even possible? Does anyone have general advice for the re-application process?
This can be subtle and depends on the schools. In particular, it might depend on the size of the institution and on how many people apply each year. It may well be that no one remembers an earlier application (large school) or that they do.
I can't recommend which of the following might be best in any given situation, but consider, at least, the following.
One strategy is just to strengthen your application in all ways that you can and apply just as if you never had done so. Of course, you may need to also account properly for the intervening year. This strategy has you not mentioning the prior history with the institution. Stress your strengths and your likelihood of success in your application and have letters of recommendation that support that idea.
But, in an opposite case, if you think you need to address the fact that you were denied entry, then, I think, you should also speak about what is different not. What has changed from a year ago, not just what is good, now. I worry that if you go too far with this it sounds like begging. But don't just mention it unless you also explicitly give the evidence that supports why they should make a different judgement this year.
If you want to contact the prior committee for information about what failed you in the past, you may get a response or not. But make it distinct from the new application itself. It may be that it was nothing more than the fact that the competition was (and remains) fierce for graduate admissions in some places. This varies by field and by time, of course.
But you can probably get a lot of information about what went wrong last time from your current professors, without even contacting the other institutions directly. Find a trusted professor and show him or her any rejection letters you got along with the material you used to support the application, especially letters of intent and statement of purpose documents. They have been through this, and may be involved, themselves, in such decisions at the current institution and can, perhaps, see how things will be read and interpreted.