Questions I've actually heard (I hire people):
Is the boss as big a pr*ck as the last place I worked (hint: I'm the boss) ?
So, you guys have really good office supplies I can steal?
You're not really going to contact my references are you?
Can I come in like noon and cut out around three - I have something else to do?
Can you put a different name on the payroll because I'm hiding from the tax people?
Oh God, you don't actually USE Novell Netware do you - that's Sooooo last century (this from someone who answered an ad for a Novell tech) ?
And one of my favorites:
Oh, I don't really want a job, I'm just doing this for a friend of mine who gets really uptight at interviews. So will you hire him?
Wear a conservative suit and tie. With shirt (I had a systems programmer show up once with just a suit and tie - these system dudes are very literal). Socks and shoes. The shoes matter the most, seriously. Be polite and cheerful. Don't lie. Show up on time - 15 minutes before your schedule. Turn your cell phone off before going in. Practice good grooming. Breath mint. Not gum.
Use commmon sense. No guns, small children, etc.
Be prepared. Beforehand, come up with a few nice compliments about the company you are interviewing for. Practice the small talk with a friend - hi, how's the weather, traffic was lousy, etc. You will probably be asked some version of "why do you want this job, why are you the one for this job" - come up with a decent answer before you start interviewing. Wierd questions are designed to put you off balance - whe you get one don't freak out, just do your best. Find out what the illegal questions are and decide beforehand what your response will be when you get one - some employers are clueless, some are devious, some are nasty.
Good luck!