Hi Erfana,
Depending on the Schools/Programs you're looking into, and the level of competition, your GPA may or may not be a big factor in how your application is viewed. Since the application process has so many 'pieces', Schools tend to want applicants with a strong overall profile. With a GPA above 3.0 (on a 4.0 scale), your grades are fine - we just won't know how they'll be viewed relative to the grades from the other applicants, but you won't be rejected because of them. As you get more and more work experience, your GPA won't matter as much.
Since you named Duke and Haas as two Schools that you might be interested in, you need to realize the volume and level of competition that you'll be up against. With those Schools, it's not just about being qualified, it's about how you "sell yourself" to the Admissions Committees. To that end, you might eventually want to talk to an Admissions Expert about your applications.
GMAT assassins aren't born, they're made,
Rich