I would get to the campus by 9:45, just to take some time to calm down, get a drink of water, etc. The admissions building is off of Bonita Ave - take a left after the Harwood dorm and then a left into the parking lot. This will be opposite the Oldenborg dorm which looks very modern.
Dress pants and a shirt are good, maybe even your "best" jeans and a nice shirt. The interview will be in an office there or in a small room (my best guess after going to other campuses). My kid didn't interview at Pomona because of distance.
Think of this as a chance to interview them too, not just them checking you out. Find out how they would differentiate themselves from other LACs you are interested in. Be curious and engaged. Don't wait passively for them to ask all the questions. If the person interviewing you is not the representative for your region, find out who is and introduce yourself. If you think the interview went well, include a photo with your ap so that your face jogs their memory. Be sure to write a quick thank you note.
Have you seen this?
http://pomona.edu/admissions/visitin...tsBrochure.pdf
This will give you the times for any campus tour you want to go on as well as a campus map. They will feed you lunch if you want.
If you are interested in sitting in on a class, contact the admissions office to see if there is a class that interests you earlier in the day or after lunch.
Have fun. Hope Pomona impresses you.