Here are 7 I have personally witnessed: 1.) Wearing a suit with the tags still on it. 2.) Telling the interviewer that "this is just temporary until"...insert your life ambition here. 3.) Bad mouth your last boss. 4.) Become combative and argue with the interviewer. 5.) Lie, a lot. 6.) Steal the interviewer's pen. 7.) Pass gas.
I've never even thought of a thank you note. Am I the only one? :zx11pissed: The worst thing I ever did on an interview was believe anything they told me. I've been told that I was absolutely perfect for about ten times more jobs than I was ever hired for.
It's been a long time since I interviewed for a job, but I always sent a thank you note. I picked up that tip in a free resume/interviewing class just before graduation.
I think number one would really show a character of unpreparedness. Sure way of botching up an interview.