I was rejected last year with a 3.55/164/out of state. This year, I did the following:
1) Moved here and established residency (you have to be here a year before school starts).
2) Retook the LSAT, improving from a 164 to a 169. UNC supposedly only looks at the high score so this should have particularly helped.
3) Wrote a new PS. My old one was more of a narrative through my resume, accentuating my lawyer like skills and aptitudes. The summer after my rejection I met with the Dean of admissions (now gone) and he told me that my PS was not good and was the reason I didn't get in, he thought. This latest PS was more of a picture into who I am as a person, with more emphasis on making an original and memorable PS. I still obviously played up some of the lawyer skill/aptitude stuff, although more subtley.
Still, this last year with a 3.55/169/in state I wasn't a slam dunk -- I got in in March when many others had already been admitted, and I was awarded zero merit money. So obviously there's still some of the picture I'm missing, so I might not be the best person to ask for specific advice.