During a telephone or face-to-face interview, the key thing to remember is the company is trying to solve a perceived problem. The company hopes that you are the solution to their problem and that is why they are interviewing you. If for any reason, the company perceives that you are not the solution to the problem, or that hiring you presents a greater risk to the company than the problem you are being interviewed to solve, you will not be hired. You must be seen as a “safe bet” and not as a work in progress or someone who will require a great deal of training before you can start solving the problem(s) you were hire to solve. Your whole function in you new position will be to reduce your manager’s pain, not increase it.
I am working with an excellent engineeering candidate that my client company flew him to their corporate headquarters for multiple interviews. The company and I perceived him to be an outstanding and very reliable individual. The company knew that he was not an exact fit for the position but he had most of the experience and training that the company wanted so they were very interested in hiring him. After two telephone interviews and three face-to-face interviews at considerable expense to the company, the company hired someone with no work experience from a local college. I believe he did not receive an offer because he was somewhat insecure and spent quite a bit of time during the interviewing process asking about training that he would be receiving instead of selling his experience and abilities. The company did not provide me with any reasons for not hiring the candidate but based on conversations with the candidate I felt that he was a little too focused on closing his self perceived gap between his experience and the job requirements instead of selling his existing abilities to the company.
Please remember that when interviewing getting the job offer is job one. That does not mean you should lie about any deficiencies or gloss them over but do not dwell on them. If the company makes you an offer, they must believe you have the requisite skills and education to be successful in the new position. If you decide later that you do not really want to work for the company, or that you do not believe you cannot perform the job satisfactorily, you can always turn the offer down.