I wish you had given more details. Are you the sole member to interview the candidates, or are you a panel member representing HR?
Interviewing as a Sole Member
If you are the sole member, then you must have a good knowledge of the "core subject" of the candidates. Suppose you are interviewing candidates for an Accounts Assistant post, then you must have adequate knowledge of Accountancy.
Interviewing as an HR Panel Member
If you are sitting from the HR side, then you should check many other things. See the certificates and all other documents submitted by the candidate. 'Confidence' can be judged by the way the candidate answers. When the candidate is asked, "Are you sure?" does he say yes, or does he fumble? Suppose you do not know whether what is answered is correct or not, make a note of it and ask your colleague in the panel if the candidate was right. If he says that the candidate was right, then the confidence is genuine. If your colleague says the answer was incorrect, then it is not merely that the candidate is wrong; he also has an attitude to bluff. A lot of information is revealed by observing the body language.
Imagine yourself in the shoes of Amitabh Bachchan and recall the way he asks questions to the contestant in the hot seat in the programme KAUN BANEGA CROREPATI.
Assessing Stability
For 'stability,' you are likely to get more clues from the candidate’s resume. Whether he has continuously worked over a long period or has had too many changes in too short a time. You can also openly ask if the candidate would leave in the event of his getting a higher salary within three or six months. However, stability is something that cannot be judged accurately. If the candidate does not like his boss or the job, then he may leave. A promise in an interview does not mean much unless agreed in writing.
There are plenty of points to consider other than CONFIDENCE and STABILITY. Please search relevant articles from Cite HR archives.
Regards,
V.Raghunathan