Stated simply, a person who does not interview well will not receive a job offer. You may prepare an exceptional resume filled with outstanding accomplishments; however, if you cannot present yourself with confidence and project a professional image in the interview, you will not get the job.
First of all, you must realize that you are not the only qualified applicant. Granted, you may believe you are, and in fact you may be, the most qualified, but if you are unable to convey this impression to the interviewer, you will receive no invitations for further interviews and most importantly, no job offer. Therefore, you must develop your interviewing skills and practice them. You must become adept at adjusting according to the interviewer's approach and at convincing him/her that you are the best candidate for the position.
Essentially, in searching for a job, you are building an image. You are "packaging" yourself and you need to project your image--to look, sound, behave and speak as that individual you are proclaiming to be. Two basic rules to remember in this pursuit are:
Be yourself to the greatest extent possible. Obtaining a job is your goal; however, try to be reasonably certain that the position you are trying to secure does, indeed fit your image and talents. Otherwise, you (and your employer) will soon become uncomfortable, creating the possibility of yet another job loss and subsequent search.
Be prepared--once you have determined the "fit", be ready to convince the interviewer that you are the very best candidate for the job. Do research and know as much about the company as possible. Above all, know you resume thoroughly--skills, talents, accomplishments, depth and breath of service to your employers---and assert this information proudly.