1. The interview is not over just because you made a weak first impression.
You can overcome a weak first impression by quickly recovering your confidence and work on making a good impression throughout the interview. You need to temporarily pretend it did not happen and mush forward. Convince yourself you will deal with the slip-up toward the conclusion of the discussion as you "end on a high note." If you make a good LAST impression, the start of the interview will be forgotten (as long as you didn't set the table on fire or ask who the ugly kids were in the picture on the interviewer's desk).
2. Your attitude toward the opportunity shows.
It might be in your body language. It could be your choice of words. It could be your tone of voice. If you are not interested (or think another opportunity is better), it will show. The trick: Tell yourself this is the best opportunity you have right now and treat it as such. You can always decide the job is not for you later. You can't turn down a job offer you don't have.
3. Be confident to the edge of cockiness.
No one hires interviewees who act like they are smarter than the interviewers. Yes, you must appear confident that you can do the job and would be the perfect candidate. But you do not have to throw it in their face. I always advise candidates: Don't tell them you are great -- tell them about great things you have done They will decide you are great on their own.
4. Just because you've made it through the previous rounds, doesn't mean you'll fly through the last one.
You start over during each round of interviews. Each interviewer has their own hot button or concerns. And of course, the higher up the food chain you go in the interviewing process, the more veto power the interviewer has. CEOs have killed candidates' chances simply because they felt the candidate "doesn't understand what the company is trying to achieve." It happens. Treat each round like the first one (with more at stake).
5. You can talk too much.
If you're not prompted to provide another example that answers a question, why would you? If you shared your BEST example, anything you say after that will be less impressive and dilute your original answer.
6. You can overdress for the interview.
I used to think the opposite until I had one of my candidates show up to an interview in cuff links. It was a casual work environment. The interviewers didn't knock the candidate for dressing up in a suit, but they wondered if he might be a little too stuffy for their culture. He dressed more casually in the second round of interviews and got the job.
7. Preparation for interviews is not overrated.
Knowing as much as you can about the interviewers, the job, and the company can only help your chances of landing the job. You should have a list of things you want to share during the interview that you think will better connect you to the opportunity and people in the company. The more you have in common, they more comfortable the interviewers will be with you.
8. Saying you are quick learner implies you are not experienced.
If you say you don't know anything about a skill or ability, but can learn it fast, you're basically saying, "No, I don't know anything about that." Instead, you might say, "I don't have experience with that, but I do know a lot about this and it is very similar." As long as this and that are truly similar, they can judge for themselves that you will pick up the desired skill quickly.
9. The interview starts in the parking lot and ends in the parking lot.
You must assume you are being evaluated by everyone you talk to the entire time you are in the building. Receptionists and admins are great at judging the soft skills (i.e., personality) of candidates. Don't assume you are waiting in the lobby for a while just because the interviewer is running late.
10. Asking questions at the end of the interview is a chance to shine even more.
By asking the "right" questions, you have a chance to show that you care about the opportunity and did your homework. It also allows you to mention some other skill or talent you have by including it in the question. For example, you could ask about a technology/tool/application you know would interest them that you are an expert at using. The question: "Has the company ever considered using XYZ for expediting the delivery of the widgets to destination? I have used it for two years and seen how it makes a difference." You also want to ask questions that prompt an interesting discussion, not a simple answer.