Most importantly, be yourself. Interviews can greatly be influenced by appearance. Dress conservatively and neat. Pay attention to details of shoes, hair well-groomed, accessories, all should be simple and meticulous. Men wear dark blue or grey suit, possible subdued pint-stripe, solid white shirt, conservative tie and shoes shined.
Women wear a two piece suit in grey or dark blue with solid white blouse and conservative shoes.
Look at photos or other object of interest in and around the office and make interesting comments about them if you are a bit nervous or having trouble breaking the ice. Stress your achievements. Sales records, awards, stories of certain deals, projects, savings achieved, systems installed, etc. Work to establish a good conversation. Always reflect before answering a question.