According to their website, admissions i based on gpa, sat's activities, volunteer experience, class rank of and the difficulty/variety of the courses taken in high school. It also depends on the campus and the major for which you are interested. NC is a very competitive college and the average student who was accepted earned a 3.5 gpa.
Check this link to NC State's Common Data Set (CDS) - the CDS lists all sorts of data about admissions. Section C lists the average SAT/ACT and GPAs of incoming freshman: