Appearance:
Clean yourself up well.. shave, put on nice and clean clothes (a bit fancier than regular street clothes but not all out as if you're going on a date) and appropriate for the position you're applazing for, i.e. no T-Shirt and Sneakers if you're going for middle management and no suit if you're "just" an office worker.
I disagree with this. Always wear a suit to the interview if it's for an office job, regardless of where in the office. You can ask about dress code during the interview.
I agree with
Professor Zoom. I had an interview last week for a Web development job. The main person interviewing me is someone I know from local fandom. I still wore a suit.
They offered me the job at the end of the interview. I started last Thursday.
(As I was leaving, my friend commented on it, and I joked, "I clean up good, don't I?" I don't think he'd ever seen me completely clean-shaven or wearing a suit in the five years we've known each other, except for perhaps at the Opening Ceremonies at Toronto Trek 19 when I was playing the role of Statler from "The Muppet Show".)