There are several important things that you should do at the beginning of an interview:
1. Give the interviewer a firm handshake and introduce yourself by using your full name.
2. Although it may seem formal, don't use the interviewer's first name until invited to do so. Make sure that you pronounce the interviewers name properly.
3. Provide the interviewer with a business card if you have one.
4. Let the interviewer initiate the conversation. Remember, you're not the interviewer.
Etiquette is sometimes considered antiquated and a little silly, but in situations like this, you really want to make the best impression possible. Following more fomal rules of interaction like using Mr. or Ms. and being deferential will really go a long way to making the best first impression possible.