(1) The receptionist will likely be your first point of contact when you come for the interview. Treat that person with courtesy and respect. He/she may be asked to share their impression of you.
(2) Don’t wear perfume, cologne, or after-shave. What you consider a pleasant scent may be sickening or overpowering to others.
(3) If offered coffee, it’s best to politely decline. You don’t want to risk spilling it on yourself, or worse, on the interviewer.
(4) Keep your interview clothing clean and pressed, ready to wear. Polish the shoes that go with it, and make sure you have the correct socks/hoisery. Check for missing buttons and broken zippers. You don’t want to be scrambling to put together an outfit the night before your interview. Try the clothing on periodically to make sure it still fits. During an extended period of unemployment, I gained 20 pounds.