Everything that everyone else has said will get you set (except knowing the 7 values of the Army...not necessary). When I was interviewed, I was lucky enough to be questioned by a very polite and down to earth officer. Remember to ALWAYS be yourself, don't over-indulge or lie because you will get caught, be calm, be humorous but focused, remember your basic manners, sit up straight, have a firm handshake, and, most importantly, be sure to "study" yourself and your past extracurricular activity, including sports and volunteer activity, before the interview, as these types of questions make up an important part of the interview.