Well I think that if we have been chosen for the interview,probably, is because we fit into the features they need .
They had red before our curriculum vitae and they know what we have done till now.
Then ,in the moment of the interview, our appearance is very important and the first impression counts a lot.Offer a neat appearance is essential in my oppinion.
And the personality ,as we can not change,I think the best is show as we are and try not to be betrayed by nerves.