No one knows that better than an administrative assistant or receptionist, with whom the person making a hiring decision often consults. Stand when you're meeting someone, and offer your hand. Don't slouch, fidget or wiggle. Keep your posture erect, standing or seating. Make small talk.
Weather is a great conversation starter.
Don't tow children, dogs or other living things to the interview. Ditto on cell phones and pagers. Ditto on gum. Don't wear too much cologne. Be a little early for the interview.