During an internal interview, the biggest, most common mistake people make is not saying enough and not putting forth enough effort.
Too many people go into this type of meeting feeling that they shouldn't or don't need to provide a lot of detail about their skills and experience because they feel the interviewer, who is usually a colleague, and maybe even a friend, already knows them.
You can't assume that just because you work with someone in one capacity, he or she knows all of the skills you can offer in another role.
Points Based Interviews
In addition, some companies, in an attempt to minimize subjectivity, use points based interviews, which means they give points for specific things each interviewee mentions.
So, if the employer is looking for 5 points in your answer to a question, and you only provide 2 points because you assume the interviewer knows you know the other important points, you will not score well on the interview even though you may be the most qualified person for the job.
No matter how well you know the colleague who is conducting the internal interview, do not assume he or she knows all about your skills. Provide as much detail as possible when you answer questions.
The interviewer wants to hear about your relevant skills, experience and accomplishments. That's why you are being interviewed!
If the supervisor didn't need to hear candidates describe their strengths in an interview, he or she would simply choose someone for the internal posting and wouldn't waste time with interviews.
You need to assume that others who are also competing for the job will be highlighting all of their marketable skills and accomplishments. So, if you fail to promote yourself effectively in an internal job interview, you will not compare well against the competition.
Although the interviewer is your colleague, he or she may not be fully aware of all of your contributions to the company. The interviewer may have forgotten about some of your major accomplishments, or he or she may not know about some skills you have that you may not use in your current role but would be valuable in the new job.
Handle internal interviews in the same way you would handle any other job interview