Once again not a favourable question, but still better than the last one.
My first job interview was for a salesman job in a computer shop called "HGspot". The biggest one there was at that time in Croatia. And it went as bad as it could. I probably said all the things I shouldn't have said. But it ende well, because I got the job. Mainly because my two friends that were working there said a few good words in my behalf.
The first thing is that you have to be prepared for the interview. I went there like I was going for a cup of cofee. Repetition is the mother of knowledge. Don't be conceited and full of yourself on the job interview. Be humble and gratefull for the chance you got. Prepare yourself and anticipate the questions you may be asked and have the right answers.
The most important is to have the knowledge of the job you are being interviewed. I was applying for a job of a salesman in a computer shop and didn't know the answer to a question what is a router. All I had to do was to go to a store that already existed, write down everything that is being sold there and learn about it. But I took it for granted and almost changed the path of my life. Who knows what I would be doing if I didn't get the job then.
So I guess the worst thing to say during a job interview is "I don't know" or "I'm not interested" or something in that manner.
And this is, like, 10 years ago!