I was looking at that myself, and I found in the CIB that some schools allow it and some don't. You should look in there, it's usually under the admissions information sections for the schools.
From what I understand its not an easy task. If you have a valid reason to defer than go ahead and contact the school and ask. If its because you want a year off and want to sit around playing Call of Duty and working part time relaxing you should have applied this year
Like the above poster said though, check the CIB, some schools allow it and some don't. I feel like some will also only let you defer for major reasons while others may be more lenient.
I know that with MSU its a very simple process, but another school I got into said only medical reasons would qualify. I think most schools are not that friendly with it.
My roomate is deferring at MSUCOM until the fall of 2011. I think all he has to do is write a short little essay, for lack of a better word, recalling what he did during his year off.