First of all, congratulations on wanting to get involved nationally!
My national GLO is quite different from NPC. We don't have CDC's, or the equivalent, mainly because we are so small. Also, our national staff is voted on & is entirely volunteer (<--- this will, hopefully, eventually change

)
And I am part of that national staff, so I thought I would try and give you some general advice. KDGirlie & ladybug gave you some great advice, listen to them!
- You do have to always be thinking of the organization first... and that means national first, chapter second in most cases.
- Definately include any leadership positions you've held at school, whether they're in your sorority or other organizations.
- Give details where you have done something very creative, or when you have solved a difficult problem "on the spot".
- Highlight your excellent time management.
- Be energetic! My contacts with GLOs that do have CDC's have taught me that those men and women are on the road constantly & have to always be up for anything. You will want to be able to relate to the women in various chapters, so being energetic & "youthful" will definately help you do that. And appearing energetic and "raring to go" to your interviewers will make them think you are up for the long trips and constant moving about
- "numbers"<-- sororities really are like businesses in a lot of ways (only way better
) I'm talking about numbers like someone applying for a promotion within their business would use.. hard facts showing your accomplishments. If you were recruitment chair, write down how much your pull of rushees grew, and how you accomplished that. If you were the sisterhood chair, write down steps you took to grow the sisterhood. If you were the New Member/Pledge trainer (I don't know the PC term for NPC
) show how the pledges improved on written test or oral tests or whatever over past years.
Hope those things help. Best of luck! Working for your sorority will be an eye-opening, exciting experience!!!