Apart from the absolutely obvious (like pee on the floor or insist on doing it stood on your head or something)

I would say the main bad things are: not making eye contact (you don't have to stare at them, but don't do the whole thing staring at your feet), answering "I don't know" to any of the questions (at least explain why you don't know), swearing (careful with that, if you;re anything like me, stuff just pops out!), lying (you always get caught out) and not asking any questions of your own (if you really can't think of any say "I did have some but we seem to have covered all those in the course of the interview." Just saying "No, not really." makes you sound like you don't care.)

Somewhere on the Web, there is a page of horror stories about interviews. Ones I can remember:

Interviewee pulled a wire on his briefcase and said it was a bomb and would explode if he didn't get a job.

Interviewee arranged a fake call with a "higher offer" in the middle of the interview.

When interviewer got phone call, interviewee pulled out girlie magazine and read it.

Tell them that your really hung over and you need to reschedule the interview.

Take a call on your cell
Yawn and then go, "Sorry, what was that again?"
Start smoking

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maybe to answer like this
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Asking "How much money am I gonna be making."

I would stay away from barfing on the interviewer.

I think a negative attitude or negative talk about former employers or co-workers would be on the top of the list of ways to sabotage yourself during an interview. If you don't like the way an interview is going or you want to cut it short, bring up a past lawsuit that involved a former employer for "sexual harrassment". I did that and it ensured that I would not be called back for a second interview. When I heard that the male employees of this construction firm used vulgar language frequently, I decided this way my way to bow out of the runnning graciously.

The worst thing is to be evasive. Try to be direct.

I once interviewed a woman who not only smelled like she hadn't washed her pantyhose in weeks, but she actually leaned over during the interview, took a dangling thread from her skirt hem in her mouth and bit it off. How repulsive!