How to impress a modeling agency.?

I would like to start looking into modeling. I have been waiting for the chance to go to the city to a couple of agencies and make an impression. How can I present myself to appear more professional and at the same time show my personality in terms of attire, makeup, intelligence, charisma, and a knowledge of modeling? I know simplicity is the way to go. I get one shot at impressing the agency and need to know how to go at it. Thank you so much!