If the offer is not extended then there is no decision for the you to make. You are not interviewing to decide if you would like to work for the company. You are not interviewing to broaden your knowledge of available opportunities. Decide if you want the job after the interview when you are home with your goals. Keep in mind that until you have the job offer, you are still the seller.
Most people move from being a seller to a buyer too fast.
Optimistic and positive attitude. Interest in the company and in the position. Indications of longevity of service. Leadership, analytical ability, continuous education and training. This person has the power to kill a offer.