An interview is a conversation between two people designed to quickly get to know the person and their experience level as it pertains to your open position. But be mindful that an interview goes both ways. The interviewee is also learning about you and your organization through what you communicate both verbally and through body language.
It's important that you know what you want to get out of the interview. Come prepared! Set some goals and establish some targeted questioning. If the position you are hiring for requires special skills make sure the questioning is designed to allow the candidate to talk about those skills and how they used them in previous companies. Saying you have a skill on your resume can mean many different things.
If you are hiring for a leadership role or service focused role then you'll need to get to know the persons personality. Your questions in this scenario should be targeted to understand how they relate to others and build high level teams.
For example, if I am in need of some major improvements in my operation I might ask a question like this: "What are your problem solving techniques and how do you manage change within an organization?"
If the position is more service based I might ask a question like this: "How do you motivate and inspire people to improve their level of service?"
You'll want to have answers to these questions thought out ahead of time. Meaning, what would be a good answer to you that will tell you this person is qualified? The answer to these or any questions could be varied so in the end you'll be assessing their answers against your pre-determined answers. Are they close? Did they say exactly what you said? Did they say it better than you or differently than you? Or was it clear they did not have the level of experience you need for this current role?
In any case, finding a qualified candidate that you believe fits the company value system is not easy. But if you come prepared you're more likely to find a candidate that will transition easily and stick around.