What not to do in an interview ...

After having conducted numerous interviews in my previous organization and conducting few in my current role, I have seen a fair share (I think!) of things that one should never do, when attending an interview. All that I am going to say here, is over and above, your technical preparation for the interview. That is a given, and is taken as a done exercise. Once you are fully prepared technically, here are some tips, that can get you through the face-to-face interview day. Quite a few technically sound people have faltered the last mile, because of these reasons. And trust me, companies, unless they are desperate, do not hire someone who is socially challenged, even if they are the best in class with respect to knowledge. Organizations run as a group of like-minded professionals. If you are neither like-minded, nor professional, there is a good chance, you may get bumped off. So here goes, my little list of things that you should not do in an interview:

Never be late for an interview . No. Never. Unless you have a really genuine reason, in which case, you should have called me and let me know the emergency. Dont smile, shrug, and say - "You know Bangalore traffic." Yes, I know Bangalore traffic, and that is why I started from home an hour early, because I had to take this interview. And I expected you to have done so too. If due to a genuine reason, you were late, and you had called in to let me know you are late, do apologize when you meet me. Gives me a good impression and makes me believe you are genuine.
Never come dressed in a jeans and t-shirt . Sometimes (rarely), a well pressed denim is ok, as long as you have a well pressed dress shirt on. It shows to me, that you are a do-er. But a t-shirt, um, no. It does not quite cut it. Remember the 'professional' part I mentioned earlier. This goes against that. Once you are hired, ask around for the dress code, and if it is ok (and in most software companies, it is OK), dress the way you want. Wear your metalica or Hell-freezes-Over tshirt. Not for your interview, na uh.
Do not talk so much that you do not let the interviewer talk . This happens a lot. The candidate has either prepared so hard, that he wants to impress me, by talking way more than me ; or he does not know much, that he talks a lot about all that he knows, so that I do not ask questions he does not know. This does not give a good impression. Answer questions to the point. Listen to the interviewer. It is very important. If you go overboard, with the above former reason, you may be thought of as textbookish.
Do not appear/behave over-confident . Humility goes a long way in projecting attitude. I do not say, appear meek and timid. Neither should you appear dumb. Behave confident of what you know. Give respect to the interviewer. Do not talk as though, it is my company's duty and life-purpose to give you a job. And as though, we would lose our life-savings, if we do not hire you. (Trust me, I have seen a couple of these cases as well.)
Do not shower admiration and adulation for my company . Yes I know, it is a good company, and that is why I still work here. If you really want to work here, and are keen about it. Let me know towards the end of the interview, in maybe a sentence or two, that you would love to work here. There, thats it. Just that. And I get that point. You are not writing a letter to the government - " I would respectfully like to inform you and your superior officers, that I wish to give my utmost best to this esteemed organization ". Nope. None of that.
Do not assume the interviewer knows all . He is human as well. If he is a manager, maybe his breadth of knowledge is wide ; but still he is not someone who will know all. When you are describing your previous job function, do not assume that I know all about that company and their products, and their source code. I was not your manager there. Do not start your sentences with "As you know ...", or, "As you are well aware that ...". As for clarifications, if you need to explain more in detail. I am sure, if I dont understand, I will ask for more details.
Proprietary knowledge. If I ask a question related to your previous work, and your answer requires that you reveal something which is proprietary knowledge, politely refuse to go into detail, because it is proprietary intellectual property. That will impress me for sure. It shows your integrity. If you are describing every data structure and algorithm in detail, I begin to doubt, whether, you would be doing the same about my algorithms, the next you interview elsewhere.
Never lie about your current salary . My HR knows your HR, and probably participate in some common Hewitt salary-level-setting exercises etc, and we all know each other well, thank you. And I will get to know your exact salary, if I needed to find out.
Try, Try, Try ... If you are asked a question, that you do not know fully, but you would like to try. Tell me, that you do not know the answer to the question, but you would like to try. And if you still do not get it, eventually (after a lot of trying), politely ask me for the answer. I will give you some marks for trying. If you give up early, you lose points. If you fake trying (you already know the answer), you lose points - yes, I can find that out too. I have a favourite puzzle, which many know the answer for, and fake trying and working out the problem. I can easily spot the fakers. I have had a few, who have told me, that they know the answer to the puzzle. Hey, that saved some time for me, trying to spot a faker. You get some points this way. Atleast you are honest.
Never fluff your work-experience. If there is something in your resume, which you did not do hands-on, but oversaw/supervised. Say so. There is nothing wrong in that. Your previous employer paid you money for that. Explain your contribution to each project in detail, and honestly. Do not fluff by claiming to have done things, that your team did.
etc etc etc ... No I am not saying that. I am saying, please dont use words like "etc etc", and "so on", "something like that", "stuff". These are things which tell me that you do not know fully, what you are talking about.
Speak slowly and clearly . Finish every sentence fully. It shows your confidence. If you do not finish your sentences, it shows your impatience.
:-( Lastly, but probably most important, do not be sullent, or morose, or tense. Be cheerful and pleasant. I should get a feeling that, having you in my team, would bring in energy to the team. My team should be happy that, I brought you in.

This is a small list of 13 (gasp, unlucky?) things, that came to my mind, when I sat down writing this list. By no means, is this list, the most complete - " How to win over your interviewer" guide. But these should defenitely get your browny points. I would again emphasize that, if it is a technical company that you are applying to, the underlying assumption is, that you know your technical competencies right. The above list is over and above that. This has been mostly written in a tech company perspective. Hope this list helps some good technical person land his perfect dream job. Good luck. The opinions expressed in this article are solely mine, and are not of my employer, in any way.