You want to arrive at your interview on time. Doing a "dry run" prior to the interview will familiarize yourself with the area and amount of time it will take you to get there, factoring in the time of day, where to park etc. 5-10 minutes before your interview, walk in and announce yourself, "i am so and so, I am here for my interview with "joe blow" and you'll probably be asked to take a seat.
I think that 10-15 minutes earlier than the said time helps the interviewee to have more time to prepare themselves. Anymore than that would likely cause the person to feel restless.
I should arrive 30 minutes earlier as it will help me to avoid any inconvinience such as traffic jam and other problems.Being there early will help me to stay calm and prepare for the best.