Few applicants are over confident which may be because of their skills and being confident they use some words which are not acceptable. Some want to show a lively attitude and use humor to impress the interviewer but that humor converts into sarcasm and applicant creates his negative impression in front of the interviewer and lose the job in the end.
Having a good track record makes some applicants arrogant and they consider themselves very important for the company after being selected for an interview. You must not have a mindset according to which company cannot be run without you. Yes you can give the company better results but it will not be ruined in your absence as it has already been running, so do not show arrogance to them.
Unable To Communicate Well
Without having ability to communicate with the confidence, you will not be able to get any job. You must be fluent n speaking and confident enough to define yourself and answer every question asked regarding you as the interview is the only way recruiter can recognize the person and can know that whether he is able to perform well in the company or not.
Dry mouth can cause problem for you during the interview. It is better to you a piece of gum before coming to the office but it must be removed before coming as well. As chewing a gum in front of the interviewer is annoying.
Usually the applicants go for the interview without having complete updates about the field in which they are appearing for the interview. They must be aware of the technology being used and what changes are coming in that. In case of less know-how, applicants are unable to reply with confident and show an impact that they do not know anything.
A very common mistake which people do is to try to make a long CV and extend it to 3 pages despite of having no experience. Hiring persons do not have enough time to see so many things which are usually irrelevant.
Asking About The Salary
IF you start asking about the salary before the interviewer say anything about that, you show that you are not interested in the job and you are just desperate for the money. You will not be concerned about the output of the company. You should always wait for the hiring manager to start negotiation about the salary, then you can talk and negotiate for it.
Thank You Note
Candidates do not bother to send an email after the interview to say a thanks to the interviewer. Even the applicant who is considered for the job after interview loses his chance. Recruiter waits to see the response of the applicant after the interview which shows that he really wants to work for the company. This is not a huge demand from the interviewer, just a single sentence is enough for the purpose.